U.S. patent application number 10/851824 was filed with the patent office on 2004-12-30 for induction generator system and method.
This patent application is currently assigned to DG Power Systems, Inc.. Invention is credited to Pendell, Larry Stuart.
Application Number | 20040263110 10/851824 |
Document ID | / |
Family ID | 26735270 |
Filed Date | 2004-12-30 |
United States Patent
Application |
20040263110 |
Kind Code |
A1 |
Pendell, Larry Stuart |
December 30, 2004 |
Induction generator system and method
Abstract
An induction generator having one or more energy windings and
one or more auxiliary windings where the auxiliary windings have
fixed and switched capacitors which are used to control the
induction generator output under variable load conditions. The
auxiliary windings are electrically and magnetically isolated from
the energy windings. The fixed capacitors are used under minimum
load condition and the switched capacitors added in response to
controls signals. The control signals are determined by analyzing
the load voltage and current and the voltage across the particular
capacitor being added. The induction generator is included in
systems where the generator is rotationally driven by an engine and
which couples the energy windings to a power grid and/or to a
variable load. The engine may also employ a controller that
receives the load current and voltage signals to determine engine
speed.
Inventors: |
Pendell, Larry Stuart;
(Elkhart, IN) |
Correspondence
Address: |
Kelly K. Kordzik, Esq.
Winstead Sechrest & Minick
P.O. Box 50784
Dallas
TX
75201
US
|
Assignee: |
DG Power Systems, Inc.
Reedsville
PA
|
Family ID: |
26735270 |
Appl. No.: |
10/851824 |
Filed: |
May 21, 2004 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10851824 |
May 21, 2004 |
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10056371 |
Jan 24, 2002 |
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6788031 |
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60264280 |
Jan 26, 2001 |
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Current U.S.
Class: |
318/794 |
Current CPC
Class: |
H02P 9/30 20130101; H02K
17/42 20130101 |
Class at
Publication: |
318/794 |
International
Class: |
H02P 001/26 |
Claims
1. A rotary induction machine comprising: a cylindrical stator; a
rotor axially rotatably positioned in the center of said stator;
rotor windings integral to said rotor; a three-phase energy winding
integral to said stator and magnetically coupled to said rotor
windings; a first three-phase auxiliary winding integral to said
stator and magnetically coupled to said rotor windings and
electrically isolated from said energy winding, said three-phase
auxiliary winding comprising three branch windings electrically
coupled forming three-phase electrical terminals; a first capacitor
electrically coupled across each of said three-phase electrical
terminals; a second capacitor coupled with a first branch switch
across a portion of a first one of said three branch windings; and
a control circuit for gating said first branch switch in response
to parameters of a first voltage corresponding to a first selected
branch winding and parameters of a voltage and a current
corresponding to said energy winding.
2. The rotary induction machine of claim 1, wherein a third
capacitor is coupled with a second branch switch across a portion
of a second one of said three branch windings, said second branch
switch gated by said control circuit in response to parameters of a
second voltage corresponding to a second selected branch winding
and said parameters of said voltage and current corresponding to
said energy winding.
3. The rotary induction machine of claim 2, wherein a fourth
capacitor is coupled with a third branch switch across a portion of
a third one of said three branch windings, said third branch switch
gated by said control circuit in response to parameters of a third
voltage corresponding to a third selected branch winding and said
parameters of said voltage and current corresponding to said energy
winding.
4. The rotary induction machine of claim 3, wherein said second,
third and fourth capacitors are not equal.
5. The rotary induction machine of claim 1, wherein said first
voltage corresponds to the voltage across said second
capacitor.
6. The rotary induction machine of claim 1, wherein said parameters
of said voltage of said energy winding comprise the output voltage
amplitude across a phase of said energy winding supplying a
load.
7. The rotary induction machine of claim 1, wherein said parameters
of said current of said energy winding comprise the output current
amplitude in a phase of said energy winding supplying a load across
a phase said energy winding.
8. The rotary induction machine of claim 1, wherein said parameters
of said voltage and current of said energy winding comprise the
phase relationship of said voltage and said current of said energy
winding resulting from a load across said phase of said energy
winding.
9. The rotary induction machine of claim 5, wherein said parameter
of said first voltage corresponds to a measure of the zero crossing
time of said first voltage.
10. The rotary induction machine of claim 1, where said branch
switch is gated on based on a first value of said parameter of said
first voltage and gated off based on a second value of said
parameter of said first voltage.
11. The rotary induction machine of claim 1, wherein said branch
switch is an electronic switch operable to conduct alternating
current (AC) when gated on.
12. (cancelled)
13. A rotary induction machine comprising: a cylindrical stator; a
rotor axially and rotatably disposed in the center of said stator;
rotor windings integral to said rotor; an energy winding integral
to said stator and magnetically coupled to said rotor windings; an
auxiliary winding integral to said stator and magnetically coupled
to said rotor windings and electrically isolated from said energy
winding; an energy storage device coupled with a branch switch
across a portion of said auxiliary winding; and a control circuit
for gating said branch switch in response to parameters of a
voltage corresponding to said auxiliary winding and parameters of a
voltage and a current corresponding to said energy winding.
14. A rotary induction machine comprising: a stator and rotor
axially disposed in the center of said stator; rotor windings
integral to said rotor; a three-phase n energy winding integral to
said stator and magnetically coupled to said rotor windings; a
three-phase auxiliary winding integral to said stator and
magnetically coupled to said rotor windings and electrically
isolated from said energy winding, said three-phase auxiliary
winding comprising three branch windings electrically coupled
forming three-phase electrical terminals; a first capacitance
electrically coupled across each of said three-phase electrical
terminals; a first switched winding integral to a first phase of
said energy winding and coupled with a first branch switch across a
portion of said first capacitance corresponding to said first
energy phase; and a control circuit for gating said first branch
switch in response to parameters of a first voltage corresponding
to a first selected branch winding and parameters a voltage and a
current corresponding to said energy winding.
15. The rotary induction machine of claim 14, wherein a second
switched winding integral to a second phase of said energy winding
is coupled with a second branch switch across a portion of a second
capacitance corresponding to said second energy phase, said second
branch switch gated by said control circuit in response to a second
voltage corresponding to a second selected branch winding and said
voltage and current corresponding to said energy winding.
16. The rotary induction machine of claim 15, wherein a third
switched winding integral to a third phase of said energy winding
is coupled with a third branch switch across a portion of a third
capacitance corresponding to said third energy phase, said third
branch switch gated by said control circuit in response to a third
voltage corresponding to a third selected branch winding and said
voltage and current corresponding to said energy winding.
Description
TECHNICAL FIELD
[0001] The present invention relates in general to induction
machines and in particular to rotating induction generators and
motors.
BACKGROUND INFORMATION
[0002] Induction machine refers to a broad class of electromagnetic
machines where force or rotational torque or electrical energy are
produced by the interaction of a driven and a generated magnetic
field and currents which occur because of induction. A rotating
induction motor or generator is one of these induction machines. To
create a rotating induction motor a cylindrically shaped stator or
stationary element has stator coils that are disposed into slots in
a magnetic material. A cylindrical rotor or rotating magnetic
material element is disposed on the same center line as the stator
and mechanically rotates on bearings placed outside the stator. The
rotor typically has slots parallel to its center line and on the
outside surface of the rotor into which conducting (typically
copper) bars, which are electrically isolated from the rotor
magnetic material, are placed. These conductor bars are then
electrically connected on both ends of the rotor creating a number
of loops of conductors wherein the axis perpendicular to the plane
formed by each loop is perpendicular to the axial center line of
the cylindrical rotor. Magnetic flux that couples through each of
these conducting loops of the rotor may induce (by magnetic
induction) currents to flow in the conductors. The interaction of
the current in the rotor conductor loops and a rotating magnetic
field is used to either create a motor (rotational torque producing
machine) or a generator (alternating current producing
machine).
[0003] Induction machines employing multiple phased electrical
excitation may easily produce a rotating magnetic field by
judicious placement of the stator coils around the cylindrical
stator and proper connection of the coils so that the direction of
the current flow in the coils creates magnetic fields that interact
with corresponding induced currents in the rotor conducting
coils.
[0004] When an induction machine is operated as a motor, then an
energy source (e.g., a three-phase power line) is connected to the
stator coils and the current that flows in the stator coils
produces a magnetic field that in turn couples with corresponding
rotor conductor loops which also produce a magnetic field. The
stator field rotates because of the fact that the stator coils are
driven by voltages with a shifted phase relationship (typically,
120 electrical degrees apart). The rotating magnetic field will
create a torque on currents induced in the rotor conductor loops
and the rotor will begin to rotate. Since the rotational speed of
the magnetic field is dictated by the frequency of the energy
source, the rotor rotation speed will lag that of the magnetic
field of the stator. Depending on the torque load on the rotor
shaft and the magnitude of the stator rotating field and the
induced currents in the rotor, the rotor accelerates up to a
rotation speed that is close to but slightly (a few percent) slower
or higher than the rotation speed of the magnetic field. In the
case of the motor, the excitation for the field of the rotor is
provided by induction from the magnetic field of the stator coils.
Multiple phased induction motors other than three phases are
possible by the proper choice of the stator and rotor coils and the
placement in the stator and rotor magnetic structures respectively.
A single phase induction motor is also possible even though a
single phase stator does not produce a rotating magnetic field. In
the single phase induction motor the stator windings and the field
windings are placed so that their axes are orthogonal (90
degrees).
[0005] Induction generators require some energy source to provide
excitation of the field windings. This excitation along with
providing mechanical rotation of the rotor conducting loops, enable
energy stored in the field of the rotor windings to be transferred
to an output or energy winding. In applications where the AC power
grid of the power company provides the excitation of the generator,
an engine may be used to rotate the rotor above a synchronous speed
to allow the generator to both supply current to a load and also
supply energy back to the grid. However, if a stand-alone operation
is desired, then some other source of excitation must be supplied
in case the power grid is disconnected or fails.
[0006] To run an induction generator in a stand-alone mode requires
that another excitation source. This may be done by providing a
field winding separate from an energy or output winding and driving
the field windings with the separate excitation source wherein the
frequency of the energy supplied to the output is governed by the
rotational speed of the rotor. If auxiliary field windings with
corresponding energy storage capacitance are added to the stator,
then a self-excited induction generator is also possible. Residual
magnetism in the rotor is usually adequate to start a process of
self-excitation. The residual magnetic field, by rotating the rotor
will excite by induction the auxiliary winding with the
corresponding capacitance and cause the capacitor to be charged to
a voltage which sometime later creates a current in the winding
inductance. This current, in turn, induces a current in the rotor
loops which again excites another auxiliary winding until the
fields in the auxiliary windings reach a steady state with an
excitation frequency dependent of the rotational speed of the
rotor. To obtain optimal efficiency, there is a phase relationship
between a field current and the corresponding output or stator
current. However, this phase relationship may be influenced by the
load current supplied by the stator winding receiving stored energy
from the rotor. To keep a self-excited induction generator
operating efficiently, the currents in the auxiliary field winding
may have to be adjusted to generate a stable output with a variable
load.
[0007] Producing a stand-alone induction generator which may supply
a load when driven from a prime mover (e.g., engine), an induction
generator operable to power condition energy from the AC power
grid, and an induction system where energy may be supplied to the
AC power grid, a variable load, or both, is desirable because of
the low cost and simplicity of the induction machine. There have
been many attempts to control the output of a self-excited
induction generator, but no commercially viable system is on the
market. There is therefore a need for an induction machine design
where all the induction machine combinations are possible while
allowing the induction machine to be controlled to produce energy
efficiently with a low distortion and stable output voltage.
SUMMARY OF THE INVENTION
[0008] An induction generator which may have various configurations
has one or more energy windings. The induction generators have one
or more energy windings which may be electrically and magnetically
isolated from each other by their relative positions as they are
wound on the stator. Additionally, auxiliary windings are placed on
the stator so that they are electrically isolated and either
magnetically isolated from or coupled to the energy windings. The
auxiliary windings have a no load capacitor placed across (in
parallel) with individual coils of the auxiliary winding. Each
winding also has a capacitor which may be selectively coupled (in
parallel) with an individual coil by an electronic AC switch in
series with the capacitor by gating the electronic AC switch with a
load control signal. Each load control signal is generated in
response to feedback signals comprising parameters of the voltage
across each capacitor, an energy winding load voltage and the
corresponding load current. Induction systems are constructed using
variations of the induction generator to produce a stand-alone
induction generator driven by a prime mover (e.g., engine) to
supply an isolated load, an induction generator wherein the field
is supplied by an AC power grid and the induction generator
supplies power to the AC grid and/or an isolated load. Also a
combination induction generator system is produced where the
induction system receives energy from or supplies energy to the AC
grid on a first energy winding and supplies an isolated load on a
second energy winding wherein the efficiency, losses, and output
voltage are regulated by feedback signals used to control of the
capacitor combinations coupled to the auxiliary windings within the
induction generator.
[0009] The foregoing has outlined rather broadly the features and
technical advantages of the present invention in order that the
detailed description of the invention that follows may be better
understood. Additional features and advantages of the invention
will be described hereinafter which form the subject of the claims
of the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] For a more complete understanding of the present invention,
and the advantages thereof, reference is now made to the following
descriptions taken in conjunction with the accompanying drawings,
in which:
[0011] FIG. 1A illustrates a cross-section of an induction machine
with a three-phase four pole energy and auxiliary winding structure
used in embodiments of the present invention where the auxiliary
winding is magnetically coupled to the energy windings and
electrically isolated from the energy windings;
[0012] FIGS. 1B and 1C are circuit diagrams illustrating
connections of individual coils for a branch energy winding and an
auxiliary winding for the induction machine in FIG. 1A;
[0013] FIG. 1D is a circuit diagram illustrating three phase Wye
configured energy and auxiliary windings by connecting the branch
windings of FIGS. 1B and 1C;
[0014] FIGS. 1E, 1F and 1G are circuit diagrams of individual
branch windings from FIGS. 1B and 1C wired to control elements to
make branch control windings;
[0015] FIG. 1H is a circuit diagram of a Wye configured auxiliary
control winding made by connecting control windings in FIGS. 1E, 1F
and 1G;
[0016] FIG. 1I is a circuit diagram of an electronic AC switch
useable in embodiments of the present invention;
[0017] FIG. 1J is a circuit diagram of another embodiment of the
present invention with a different connection of control
elements;
[0018] FIGS. 1K and 1L are circuit diagrams of multiple
magnetically coupled control windings according to the topology of
FIG. 1H used in embodiments of the present invention to provide
higher resolution of control;
[0019] FIG. 2A illustrates a cross-section of an induction machine
with auxiliary and energy coils wound enabling a two single phase
two pole energy windings and a three-phase auxiliary winding
structure where the auxiliary winding is magnetically coupled to
both the energy windings and electrically isolated from both the
energy windings;
[0020] FIG. 2B is a circuit diagram illustrating a connection of
the coils in FIG. 2A according to embodiments of the present
invention;
[0021] FIG. 2C is a circuit diagram of branch auxiliary windings
according to the embodiment of FIG. 2B;
[0022] FIG. 2D is a circuit diagram of the two single phase energy
windings and a three-phase Wye configured auxiliary winding
according to the embodiment of FIGS. 2B and 2C;
[0023] FIGS. 2E, 2F, and 2G are circuit diagrams of individual
branch windings from FIGS. 2B and 2C wired to control elements to
make branch control windings according to one embodiment of the
present invention;
[0024] FIG. 2H is a circuit diagram of a Wye configured auxiliary
control winding made by connecting control windings in FIGS. 2E,
2F, and 2G;
[0025] FIG. 2I is a circuit diagram of another embodiment of the
present invention with a different connection of control
elements;
[0026] FIGS. 2J and 2L are circuit diagrams of multiple
magnetically coupled control windings according to the topology of
FIG. 2H used in embodiments of the present invention to provide
higher resolution of control;
[0027] FIG. 2M is an alternate circuit configuration of the control
winding 226 in FIG. 2H with inductances in a Delta configuration
and un-switched capacitors in a Wye configuration;
[0028] FIG. 2N is another alternate circuit configuration of the
control winding 226 in FIG. 2H with inductances in a Delta
configuration and un-switched capacitors in a Delta
configuration;
[0029] FIG. 2P is another alternate circuit configuration of the
control winding 226 in FIG. 2H with inductances in a Wye
configuration and un-switched capacitors in a Delta
configuration;
[0030] FIG. 3A illustrates a cross-section of an induction machine
configured to enable two three phase two pole energy windings and a
three phase two pole auxiliary winding structure used in
embodiments of the present invention where the auxiliary winding is
magnetically coupled to one energy winding and electrically
isolated from both energy windings;
[0031] FIGS. 3B and 3C are circuit diagrams illustrating
connections of individual coils for branch energy and auxiliary
windings used in an embodiment of the present invention in FIG.
3A;
[0032] FIG. 3D is a circuit diagram illustrating two three phase
Wye configured energy windings and a single three phase Wye
configured auxiliary winding magnetically coupled to an energy
winding;
[0033] FIGS. 3E, 3F, and 3G are circuit diagrams of individual
branch windings from FIGS. 3B and 3C wired to control elements to
make branch control windings according to one embodiment of the
present invention;
[0034] FIG. 3H is a circuit diagram of a Wye configured auxiliary
control winding made by connecting control windings in FIGS. 3E,
3F, and 3G;
[0035] FIG. 3I is a circuit diagram of another embodiment of the
present invention with a different connection of control
elements;
[0036] FIGS. 3J and 3L are circuit diagrams of multiple
magnetically coupled control windings according to the topology of
FIG. 3H used in embodiments of the present invention to provide
higher resolution of control;
[0037] FIG. 4A illustrates a cross-section of an induction machine
configured to enable two single phase two pole energy windings and
a three phase auxiliary winding structure used in embodiments of
the present invention where the auxiliary winding is magnetically
coupled to one of the energy windings and electrically isolated
from both the energy windings;
[0038] FIG. 4B is a circuit diagram illustrating a connection of
energy and auxiliary coils according to the embodiment of the
present invention in FIG. 4A;
[0039] FIG. 4C is a circuit diagram illustrating connections of
individual coils for branch energy and auxiliary windings used in
an embodiment of the present invention in FIG. 4A;
[0040] FIG. 4D is a circuit diagram illustrating a three phase Wye
configured auxiliary windings and two single phase Wye configured
energy winding with one of the single phase energy windings
magnetically coupled to an energy winding;
[0041] FIGS. 4E, 4F, and 4G are circuit diagrams of individual
branch windings from FIG. 3C wired to control elements to make
branch control windings according to one embodiment of the present
invention;
[0042] FIG. 4H is a circuit diagram of a Wye configured auxiliary
control winding made by connecting control windings in FIGS. 4E,
4F, and 4G;
[0043] FIG. 41 is a circuit diagram of another embodiment of the
present invention with a different connection of control
elements;
[0044] FIGS. 4J and 4L are circuit diagrams of multiple
magnetically coupled control windings according to the topology of
FIG. 4H used in embodiments of the present invention to provide
higher resolution of control;
[0045] FIG. 5A is a diagram of three phase currents or voltages
which supplied to or resulting from embodiments of the present
invention with three phase energy or auxiliary windings;
[0046] FIG. 5B is a diagram of a portion of a rotor from FIG. 1
showing a connection of energy coils and the corresponding current
flow and resulting magnetic flux lines according to one connection
of energy coils;
[0047] FIG. 6A illustrates a cross-section of an induction machine
with a three phase four pole energy and auxiliary winding structure
used in embodiments of the present invention where the auxiliary
winding is magnetically and electrically isolated from the energy
winding;
[0048] FIGS. 6B and 6C are circuit diagrams illustrating
connections of individual coils for branch energy and auxiliary
windings used in an embodiment of the present invention in FIG.
6A;
[0049] FIG. 6D is a circuit diagram of a three phase Wye configured
energy and auxiliary winding made by connecting circuit elements of
FIGS. 6B and 6C;
[0050] FIGS. 6E, 6F, and 6G are circuit diagrams of individual
branch windings from FIGS. 6B and 6C wired to control elements to
make branch control windings according to one embodiment of the
present invention;
[0051] FIG. 6H is a circuit diagram of a Wye configured auxiliary
control winding made by connecting control windings in FIGS. 6E,
6F, and 6G;
[0052] FIG. 6I is a circuit diagram of another embodiment of the
present invention with a different connection of control
elements;
[0053] FIGS. 6J and 6L are circuit diagrams of multiple
magnetically coupled control windings according to the topology of
FIG. 6A used in embodiments of the present invention to provide
higher resolution of control;
[0054] FIG. 7A is a block diagram of a system operating as a
stand-alone self-excited induction generator supplying a variable
load according to embodiments of the present invention;
[0055] FIG. 7B is a block diagram of a system operating where
multiple energy windings and an auxiliary winding are used to
implement a motor/generator combination supplying a variable load
according to embodiments of the present invention;
[0056] FIG. 7C is a block diagram of another system according to
embodiments of the present invention;
[0057] FIG. 7D is an embodiment of the present invention
illustrating the use of combination energy/control windings.
[0058] FIG. 8 is a block diagram of a combination system of an
induction machine, according to the embodiment of the present
invention, operating as a stand-alone self-excited induction
generator, a driven generator feeding multiple loads or a
blink-less generator system supplying a variable load;
[0059] FIG. 9 is a block diagram of a combination system of an
induction machine, according to another embodiment of the present
invention, operating as a stand-alone self-excited induction
generator, a driven generator feeding multiple loads or a
blink-less generator system supplying a variable load;
[0060] FIG. 10A is a circuit diagram of analog circuits operable to
generate load voltage and current signals;
[0061] FIG. 10B is a block diagram of a generator controller
according to embodiments of the present invention;
[0062] FIG. 11 is a block diagram of a engine controller according
to embodiments of the present invention;
[0063] FIG. 12 is a block of connections between a master
controller and a engine and a generator controller;
[0064] FIG. 13 is a flow diagram of an engine start sequence used
embodiments of the present invention;
[0065] FIG. 14 is a flow diagram of another engine start sequence
used embodiments of the present invention;
[0066] FIG. 15 is a flow diagram of an engine control sequence used
in embodiments of the present invention;
[0067] FIG. 16 is a flow diagram of an generator control sequence
used in embodiments of the present invention; and
[0068] FIG. 17 is a flow diagram method steps in controlling an
induction machine according to embodiments of the present
invention.
DETAILED DESCRIPTION
[0069] In the following description, numerous specific details are
set forth to provide a thorough understanding of the present
invention. However, it will be obvious to those skilled in the art
that the present invention may be practiced without such specific
details. In other instances, well-known circuits have been shown in
block diagram form in order not to obscure the present invention in
unnecessary detail. For the most part, details concerning timing
considerations and the like have been omitted in as much as such
details are not necessary to obtain a complete understanding of the
present invention and are within the skills of persons of ordinary
skill in the relevant art.
[0070] Refer now to the drawings wherein depicted elements are not
necessarily shown to scale and wherein like or similar elements are
designated by the same reference numeral through the several
views.
[0071] Refer to FIG. 1A for an explanation of terminology that will
be used throughout this description to explain embodiments of the
present invention. FIG. 1A is a cross-section of an induction
machine used in one of the embodiments of the present invention.
Coils on like designated "teeth" (e.g., A, B, C, AX, BX, CX) may be
electrically coupled in series or parallel with the current flow
direction dictating the electrical terminal connections to create
particular magnetic poles (North or South) on a give tooth. In the
figures a number on a tooth (e.g., 101 in FIG. 1A) designates a
particular tooth and the letters (e.g., A) designates a particular
coil wound on that tooth (e.g., A101, AX101). For example, see FIG.
5B. This graphic representation is not meant to describe how actual
motors are wound in practice, but rather to show the topology of
the coils and the different magnetic and electrical configurations
covered in the present invention.
[0072] Coils with like letter designators are coupled together to
create a winding branch of either a single phase winding (only one
pair of input or output terminals) or a three phase winding (three
of four input or output terminals) depending on whether it is a
three phase Wye or Delta configuration. The terminology and
convention used in the figures are used to simplify the explanation
of embodiments of the present invention.
[0073] The "X" designator on a coil (e.g., AX) is used to indicate
an "auxiliary" or control coil for auxiliary windings. Single
letter designators (e.g., A, B, C) designate "energy" coils used to
make input (motor) or output (generator) energy windings. Each coil
has two terminals, for example, coil A101 has terminals A11 and
A12. A second "A" coil, for example, coil A104 has terminals A21
and A22. Designating the coil terminals in this manner enables the
different electrical coil connections to be more easily
understood.
[0074] FIG. 5B illustrates coupling coils A101 and A104 to create a
North magnetic pole at tooth 101 and a South magnetic pole at tooth
104. Terminals A12 and A22 are electrically connected so that the
direction of coil current 502, for an applied potential between A11
and A21, creates flux lines 501. Since the voltage potential
between A11 and A21 results in an alternating current (AC) circuit,
the flux lines 501 represent a direction only in a particular time
interval where the potential difference from A11 to A21 is
positive.
[0075] FIG. 1A illustrates an embodiment of the present invention
where the inductive machine 100 is configured so that the coils
(A101, A104, A107, A110, B102, B105, B108, B111, C103, C106, C109,
C112) may be interconnected to create an induction machine with
three phase (A, B, C) energy windings in a four-pole configuration.
Likewise, "auxiliary coils" (AX101, AX104, AX107, AX110, BX102,
BX105, BX108, BX111, CX103, CX106, CX109, CX112) may be
interconnected to create three phase auxiliary windings that are
magnetically coupled to (wound on the same teeth) but electrically
isolated from the energy windings. FIG. 5A is a waveform diagram of
three phase waves A520, B521 and C522 (voltage or current)
approximately 120 electrical degrees apart.
[0076] Induction machine 100 has a stator 120 with "teeth" 101-112
on which corresponding coils, A101, A104, A107, A110, B102, B105,
B108, B111, C103, C106, C109, C112, AX101, AX104, AX107, AX110,
BX102, BX105, BX108, BX111, CX103, CX106, CX109, and CX112 are
wound. Rotor 117 is rotatably disposed within and on the center
axis of the stator 120 and rotates on shaft 118. Rotor 117 has
coils (e.g., rotor coils 119) wound in slots on it outer surface.
Magnetic flux lines (e.g., like 501 in FIG. 5B) couple to the rotor
117 and thus to rotor coils through the circumferential air gap 199
between the rotor 117 and stator 120. Rotor coils like exemplary
coils 119 are typically shorted loops which create what is termed a
"squirrel cage" rotor design.
[0077] FIG. 1B is a circuit diagram of the connection sequence for
the coils (e.g., A101, A104, A107, A110) on stator teeth 101-112.
The particular electrical connection of the terminals, A12 to A22
and A21 to A31 and A32 to A42, for coils A101, A104, A107, A110,
creates a North magnetic pole at tooth 101 and a South magnetic
pole at tooth 104 for a current flow into terminal A11 and out of
terminal A42. The connection of coils A101, A104, A107, A110, in
FIG. 1B creates a branch winding BA130. A same connection sequence
for coils B102, B105, B108, B111 (B12 to B22 and B21 to B31 and B32
to B42) creates a branch winding BB140. For a current flow into
terminal B11 and out of terminal B41, branch winding BB140 creates
a North magnetic pole at tooth 102 and a South magnetic pole at
tooth 105. Likewise a same connection sequence for coils C103,
C106, C109, and C112 (C12 to C22 and C21 to C31 and C32 to C42)
create a branch winding BC150. For a current flow into terminal C11
and out of terminal C41, branch winding BC150 creates a North
magnetic pole at tooth 103 and a South magnetic pole at tooth
106.
[0078] FIG. 1C is a circuit diagram of the connection sequence for
the auxiliary coils AX101, AX104, AX107, AX110 to create auxiliary
branch winding BAX160, auxiliary coils BX102, BX105, BX108, BX111
to create auxiliary branch winding BBX 170, and auxiliary coils
CX103, CX106, CX109, CX112 to create auxiliary branch winding
BCX180. The circuit diagrams in FIG. 1B and FIG. 1C illustrate the
symmetrical wiring employed in winding induction machines used in
embodiments of the present invention. It should be noted that the
branch windings (e.g., BAX160, BBX170 and BCX180) are a series
connection of individual inductances that have connections that may
be wired outside the stator 120 to enable the connection of
additional circuit elements. For example, the connection node of
exemplary terminals A12 and A22 may have a connection wired so that
additional external components may be used. Embodiments of the
present invention use the partitioning of the auxiliary branch
windings (e.g., BAX160, BBX170 and BCX180) to create control
windings for induction generator configurations.
[0079] FIG. 1D is a circuit diagram that illustrates the magnetic
and electrical structure created when branch energy windings BA130,
BB140 and BC150 are configured as a three phase Wye configured
winding 122 by connecting terminals A41, B41 and C41, creating a
node 123, and branch auxiliary windings BAX160, BBX170 and BCX180
are also configured as a three phase Wye configured winding 124 by
connecting terminals AX41, BX41 and CX41 creating note 125. Nodes
122 and 125 are electrically neutral potential points with respect
to the three phase windings 122 and 124, respectively, and may be
used in embodiments of the present invention as ground or reference
points. Lines 121 indicate that the three phase energy winding 122
and the three phase auxiliary winding 124 are magnetically coupled.
Electrical terminals A11, C11 and B11 and node 123 may be wired to
external inputs or outputs (not shown). Likewise, electrical
terminals AX11, CX11 and BX11 and node 125 may be wired to external
circuits to create a control winding according to embodiments of
the present invention.
[0080] FIG. 1E, is a circuit diagram of the inductance elements
(coils) AX101, AX104, AX107, and AX110 which make up auxiliary
branch winding BAX160, as described in FIG. 1C, wired to form
control branch winding 141 according to embodiments of the present
invention. Coils AX101 and AX104 form a series inductance L1 142,
and coils AX107 and AX 110 form a series inductance LS1 143. This
is the partitioning of an auxiliary winding discussed herein. The
connection of inductances L1 142 and LS1 143 creates a circuit node
144. A series circuit connection of capacitor CX1 145 and
electronic AC switch SX 148 are connected from node 144 to
electrical terminal AX41 on coil AX 110. A second capacitor CX0 146
is connected from electrical terminal AX11 on coil AX101 to
terminal AX41 on coil AX110. Electronic AC switch SX 148 has a
control input CN1 147 which is used in embodiments of the present
invention to switch capacitor CX1 145 into and out of control
branch winding 141.
[0081] FIG. 1F is a circuit diagram of the inductance elements
(coils) BX102, BX105, BX108, and BX111 which make up auxiliary
branch winding BBX170, as described in FIG. 1C, wired to form
control branch winding 151 according to embodiments of the present
invention. Coils BX102 and BX105 form a series inductance L2 152,
and coils BX108 and BX111 form a series inductance LS2 153. This is
the partitioning of an auxiliary winding discussed herein. The
connection of inductances L2 152 and LS2 153 creates a circuit node
154. A series circuit connection of capacitor CX2 155 and
electronic AC switch SX 158 are connected from node 154 to
electrical terminal BX41 on coil BX111. A second capacitor CX0 156
is connected from electrical terminal BX11 on coil BX102 to
terminal BX41 on coil BX111. Electronic AC switch SX 158 has a
control input CN2 157 which is used in embodiments of the present
invention to switch capacitor CX2 155 into and out of control
branch winding 151.
[0082] FIG. 1G is a circuit diagram of the inductance elements
(coils) CX103, CX106, CX109, and CX112 which make up auxiliary
branch winding BCX180, as described in FIG. 1C, wired to form
control branch winding 161 according to embodiments of the present
invention. Coils CX1O3 and CX106 form a series inductance L2 162,
and coils CX109 and CX112 form a series inductance LS2 163. This is
the partitioning of an auxiliary winding discussed herein. The
connection of inductances L2 162 and LS2 163 creates a circuit node
164. A series circuit connection of capacitor CX2 165 and
electronic AC switch SX 168 are connected from node 164 to
electrical terminal CX41 on coil CX111. A second capacitor CX0 166
is connected from electrical terminal CX11 on coil CX103 to
terminal CX41 on coil CX112 Electronic AC switch SX 168 has a
control input CN3 167 which is used in embodiments of the present
invention to switch capacitor CX3 165 into and out of control
branch winding 161.
[0083] FIG. 1H is a circuit diagram illustrating a three phase
control winding 126 according to embodiments of the present
invention made by interconnecting branch control windings 141, 151
and 161 described in FIGS. 1E, 1F, and 1G respectively. Control
winding 126 is configured as a three phase Wye winding. The
electronic switches SX 148, 158 and 168 along with their
corresponding switched capacitors CX1 145, 155 and 165 are
designated as control elements 750, 760 and 770 respectively. While
the particular control elements are shown as having a
bi-directional electronic switch (e.g, SX 148, 158 and 168) for
connecting and disconnecting capacitors CX1 145, CX2 155 and CX3
165, a continuously electronically controllable capacitor would
still be within the scope of the present invention.
[0084] Returning to FIG. 1A, induction machine 100 may be operated
as a generator by coupling shaft 118 to an engine which is operable
to apply torque and thus rotate the rotor 117 at a controlled
speed. If the rotor 117 magnetic material has a residual
magnetization or is initially magnetized by an external potential,
changing flux in the rotor coils (e.g., coils 119) will cause rotor
coil currents to flow by induction. The induced rotor coil current
will likewise generate a magnetic field which will couple to the
coils of control winding 126 and produce current flow in control
winding 126 also by induction. Capacitors CX0 146, 156, and 166
will charge and store energy and later return this energy to their
corresponding coils. The capacitors CX0 146, 156, and 166 are sized
so that they are resonant at a desired frequency (e.g., 60 Hz) with
their corresponding branch control coils. The combination of this
resonant circuit and the rotational mechanical energy causes the
control windings to build up a steady rotating flux field in stator
120. The induction interaction of this control winding 126 field
with rotor 117 delivers energy to energy windings 122 when the
rotor is rotated at a speed determined by its stator and rotor
design (number of poles, teeth and rotor coils). Adding capacitors
to the energy windings or to auxiliary windings creates a
self-excited induction generator. However, the particular
capacitors that need to be added are dependent on the magnitude and
the nature of the load that the induction generator is supplying.
If capacitors CX0 146, 156, and 166 were to be varied, then
additional capacitance would have to be supplied in parallel. This
may result in excess current through a switch if the switched
capacitor was uncharged, depending on the voltage state of the
un-switched capacitor. Embodiments of the present invention isolate
the fixed capacitors (CX0 146, 156, and 166) and the switched
capacitors (CX1 145, CX2, 155 and CX3 165) by partitioning the
control winding. The inductance of the windings will prevent
uncontrolled currents from flowing.
[0085] Capacitors CX0 146, 156, and 166 may be equal values for a
particular induction generator 100 electrical load connected to
three phase energy winding 122 (FIG. 1D). However, it has been
determined that it is the actual summation of capacitances applied
to the energy or auxiliary (control) windings that determine
optimum operation for a given induction generator design and load
condition. While it may be convenient for CX0 146, 156, and 166 to
be of equal values for the embodiment described in FIGS. 1A-1L, it
is not a requirement.
[0086] Capacitors CX0 146, 156, and 166 may be sized for an optimum
condition when a minimum load is connected to energy winding 122.
The resonant design of the branch control windings and their
corresponding parallel capacitors CX0 146, 156 and 166, result in a
self-excited induction generator. If the control winding has
capacitors (CX0 146, 156, and 166) sized for a 60 Hz resonance,
then rotating the rotor 117 at a speed (revolutions per minute
(RPM)) will produce a 60 Hz self-excited induction generator. If
the energy winding 122 is coupled to a variable load, then as the
load varies, the interaction of the load current with the induced
currents in the control windings results in a non-optimum
operation. If the capacitors (CX0 146, 156, and 166) could also be
varied in response to a varying load, then the optimum operation of
the induction generator 100 could be maintained.
[0087] Control winding 126 is used in embodiments of the present
invention to switch in capacitances (CX1 145, CX2 155 and CX3 165)
in response to the changing parameters of the load voltage and load
current of a variable load coupled to energy winding 122. By using
unequal values for capacitors CX1 145, CX2 155 and CX3 165, the
total capacitance on control winding 126 may be made to vary in
discrete steps.
[0088] In one embodiment of the present invention, all the branch
control windings BAX160, BBX170 and BCX180 and their partitions are
equal and the capacitors CX0 146, CX0 156, and CX0 166 are likewise
equal. However, the capacitors CX1 145, CX2 155 and CX3 165 may not
be equal but have a summation equal to a capacitance required for a
maximum load condition. One possible configuration for capacitors
CX1 145, CX2 155 and CX3 165 has the capacitor values related by a
factor of two; CX2 155 is equal to twice CX1 145, and CX3 165 is
equal to twice CX2 155. By appropriate gating of the switch
elements SX 148, SX 158 and SX 168, eight different capacitor
values may be realized for control winding 126. In this manner, a
minimum to maximum load variation may be optimized with a
particular capacitor value of one part in eight. Embodiments of the
present invention have demonstrated that the capacitance of the
control winding 126 need not have the same capacitance on each
branch winding to have a desired result, rather, only the magnitude
of the capacitance on the entire auxiliary winding need be
controlled. In this manner, a dynamic load may be monitored by
sensing parameters of the load voltage and current to determine
which combination of capacitance to switch into the control winding
126 as the load varies over a minimum to maximum range. By
partitioning the control winding 126 into a portion (e.g., LS1 143
with a switched capacitor (e.g., CX1 145) and one without a
switched capacitor (e.g., L1 142), the transient currents through
the switched capacitors may be minimized during switching. In one
embodiment of the present invention, the voltage across the branch
control winding inductance (e.g., LS1 143) is monitored so that
capacitor CX1 145 is switched in only when its terminals are at or
near a zero voltage condition. Embodiments of the present invention
that use a monitored voltage as the control parameter to switch the
capacitors may use hysteresis when switching in the discrete
capacitors to prevent a "hunting" condition where the capacitance
is not the required exact value for a given load condition. Other
embodiments may use a load current value to determine how much
capacitance to switch into the control winding 126. In this
embodiment, a switched in value of capacitance would remain
connected as long as the load current was above a prescribed limit.
Using current may not require the same level of hysteresis as when
using voltage. Other embodiments of the present invention use more
complex algorithms where combinations of load voltage and currents
are used to determine how much capacitance to switch into a control
winding 126. For example, along with load voltage and current
amplitude, the phase angle between the load voltage and current may
also be used to determine an optimum control winding 126
capacitance.
[0089] FIG. 1I is a circuit diagram of a triac 128 which may be
used as the AC electronic switch 148, 158, 168 according to
embodiments of the present invention. Triac 128 has an anode 127
and a cathode 129 and a control gate 130. By applying an
appropriate gate voltage to gate 130, the triac 128 may be made to
conduct in either direction until the current goes through a zero
value at which time it is gated on again and current will resume in
the other direction. Modem triacs 128 may be supplied from the
manufacturer with additional circuitry that may determine a zero
voltage condition before supplying a gate signal to control gate
130. While parameters of a load coupled to induction generator 100
may be used to signal that a capacitor value is needed, the actual
timing of the signal applied to an electronic switch (triac 128)
may be modified by the circuitry supplied from a manufacturer of
the triac 128.
[0090] FIG. 1J is a circuit diagram of control winding 131 where
control elements 750, 760 and 770 are place across a branch control
inductance LS2 153. The control winding 131, in this example, is
shown to have the same branch elements as control winding 126 (see
FIG. 1H). In this manner, control elements 750, 760 and 770 may
have the same internal component values as when used for control
winding 126. Therefore, control winding 131 can be used in the same
manner as control winding 126. However, since the capacitors (CX1
145, CX2 155 and CX3 165 in control elements 750, 760 and 770 in
FIG. 1H) are added with no inductive isolation, more care would
have to be taken to guarantee that the capacitor terminal voltages
are very near a zero value to eliminate excessive transient
currents. While this embodiment has a more stringent switching
requirement, switching the capacitors within control winding 131
across only one inductive element (LS2 152) works and is within the
scope of the present invention.
[0091] FIGS. 1K and 1L are circuit diagrams of another embodiment
of the present invention. In this embodiment, a control winding 140
is partitioned into two control windings 150 and 160. Control
windings 150 and 160 may be wound according to the topology for
control winding 126. Control winding 140 can be used in a same
manner as control winding 126 or 131. For example, branch winding
element L2 178 would be wound on the same stator teeth in the same
way as L21 138, however their respective electrical terminals would
be kept isolated creating two electrically independent but
magnetically coupled elements. In the same manner, branch winding
elements LS2 177 and LS21 137 would be on the same stator teeth
again keeping their respective electrical terminals isolated.
Repeating this for all three of the three phase branch control
windings enables two magnetically coupled control windings that are
electrically isolated. Branch windings may be designed so that the
operation of a branch comprising L2 178 and LS2 177 and
corresponding capacitor C0 181 and a magnetically coupled branch
L21 138, LS21 137 and capacitor C00 191 is the same as
corresponding branch comprising L2 152, LS2 153 and CX0 156 of
control windings 126 (FIG. 1H) and 131 (FIG. 1J). If the
partitioned control winding 140 is made to be equivalent to control
winding 126 or control winding 131 in this manner on all three
branches, an extra level of control is possible allowing for a
finer control of added capacitance of a load range.
[0092] Control winding 140 would represent one level of control.
Non-switched capacitors C0 171, C0 181 and C0 187 would operate
with branch windings L1 174, LS1 175, L2 178, LS2 177, L3 186 and
LS3 183 to set a first circuit state for control winding 150, and
switching in capacitors C1 173, C2 183 and C3 188 enables seven
additional circuit states for control winding 150. Switched
capacitors C1 173, C2 183 and C3 188 are alternately switched into
control winding 150 with switch elements 176, 179, and 184
respectively. Switch element 176, 179, and 184 have control inputs
CN1 172, CN2 180 and CN3 182 respectively.
[0093] Control winding 160 would represent a second level of
control. Non-switched capacitors C00 189, C00 191 and C00 197 would
operate with branch windings L11 134, L21 138, L31 196, LS11 135,
LS21 137 and LS31 193 to set a first circuit state for control
winding 160, and switching in capacitors C11 133, C21 193 and C31
198 sets seven additional circuit states for control winding 160.
Switched capacitors C11 133, C21 193 and C31 198 are alternately
switched into control winding 160 with switch elements 136, 139,
and 194 respectively. Switch elements 136, 139, and 194 have
control inputs CN11 132, CN21 190 and CN31 192 respectively.
[0094] Auxiliary windings 150 and 160 are magnetically coupled in
this embodiment of the present invention, and the state of control
winding 160, when no switch elements are conducting, would add to
the first circuit state of control winding 150. The first circuit
state of control windings 150 and 160 along with the seven
additional circuit states of control winding 150 generate eight
circuit states. By switching capacitors 160, an additional seven
circuit states allow the combination of control windings 150 and
160 to generate a total of 56 circuit states. Since control
windings 150 and 160 magnetically work together, a finer resolution
of control is achieved. This method of partitioning a control
winding for an induction generator, according to embodiments of the
present invention, may be extended to more than two partitions.
Additional partitions are determined only by physical winding
limitations and the packaging of the individual capacitors and
switching elements.
[0095] FIG. 2A is a cross-section of another induction machine 200
according to embodiments of the present invention. The stator 120,
rotor 117 and rotor windings 119 are given the same designators as
in FIG. 1A. Since the teeth of the stator are wound differently in
this embodiment, the teeth are give different designators.
Induction machine 200 is wound as having two single phase windings
(A and B) and one three phase (AX, BX and CX) auxiliary winding.
Induction machine 200 has stator teeth 201-212. Coils A201, A202,
A203, A207, A208, and A209 are wound on teeth 201, 202, 203, 207,
208 and 209 to produce two magnetic poles (North and a South).
Likewise, coils B204, B205, B206, B210, B211, and B212 are wound on
teeth 204, 205, 206, 210, 211, 212 respectively to create two
magnetic poles (North and a South). Auxiliary coils AX201, AX204,
AX207, and AX210 are wound on teeth 201, 204, 207 and 210,
auxiliary coils BX203, BX205, BX208, BX211 are wound on teeth 203,
205, 208 and 211, and auxiliary coils CX202, CX206, CX209, CX212
are wound on teeth 202, 206, 209, and 212 to each create 4 magnetic
poles (two North and two South). The electrical terminal
designations follow the same convention as described in FIG.
1A.
[0096] FIG. 2B is a circuit diagram illustrating how the individual
coils are connected and the magnetic couplings for the induction
machine 200. The coils A201, A202, A203, A207, A208, and A209 are
connected in their electrical terminal sequence shown in FIG. 2B to
create a two pole single phase energy winding BA201. Likewise, a
second two pole single phase energy winding BB202 is created by
connecting the electrical terminals of the energy coils B201, B202,
B203, B207, B208, and B209 in the sequence shown. Auxiliary coils
AX201, BX202, CX203, AX207, BX208, and CX209 are magnetically
coupled (wound on the same stator tooth) to energy coils A201,
A202, A203, A207, A208, and A209. The auxiliary coils AX204, BX205,
CX206, AX210, BX211, and CX212 are magnetically coupled to
corresponding energy coils B201, B202, B203, B207, B208, and B209.
Auxiliary coils AX201, BX202, CX203, AX207, BX208, CX209 AX204,
BX205, CX206, AX210, BX211, and CX212 are connected with the
electrical terminal sequence shown to create a three branch
auxiliary windings with electrical terminals AX11, BX11, CX11,
AX41, BX41, and CX41.
[0097] FIG. 2C is a circuit diagram of the branch windings of the
auxiliary coils shown in FIG. 2B. Auxiliary coils AX201, AX204,
AX207 and AX210 form auxiliary branch winding BAX260. Auxiliary
coils BX202, BX205, BX208 and BX211 form auxiliary branch winding
BBX270. Auxiliary coils CX203, CX206, CX209 and CX212 form
auxiliary branch winding BCX280.
[0098] FIG. 2D is a circuit diagram illustrating the structure of
the energy windings and the auxiliary windings according to the
embodiment in FIGS. 2A-2K. Single phase energy winding BA201 has
output terminals A11 and A61 and is magnetically coupled
(illustrated by lines 223) to three phase Wye configured auxiliary
winding 221. Auxiliary winding 221 is created by connecting branch
auxiliary windings BAX260, BBX270 and BCX280 with their respective
electrical terminals AX41, BX41 and CX41 creating circuit node 224.
Three phase auxiliary winding 221 is also magnetically coupled
(illustrated by lines 225) to a second single phase energy winding
BB202 with electrical terminals B11 and B61.
[0099] FIG. 2E is a circuit diagram of the inductance elements
(coils) AX201, AX204, AX207, and AX210 which make up auxiliary
branch winding BAX260, as described in FIG. 2C, wired to form
control branch winding 241 according to embodiments of the present
invention. Coils AX201 and AX204 form a series inductance L1 242,
and coils AX207 and AX210 form a series inductance LS1 243. This is
the partitioning of an auxiliary winding discussed previously
herein. The connection of inductances L1 242 and LS1 243 creates a
circuit node 244. A series circuit connection of capacitor CX1 245
and electronic AC switch SX 248 is connected from node 244 to
electrical terminal AX41 on coil AX210. A second capacitor CX0 246
is connected from electrical terminal AX11 on coil AX201 to AX41 on
coil AX210. Electronic AC switch SX 248 has a control input CN1 247
which is used in embodiments of the present invention to switch
capacitor CX1 245 into and out of branch control winding 241.
[0100] FIG. 2F is a circuit diagram of the inductance elements
(coils) BX202, BX205, BX208, and BX211 which make up auxiliary
branch winding BBX270, as described in FIG. 2C, wired to form
control branch winding 251 according to embodiments of the present
invention. Coils BX202 and BX205 form a series inductance L2 252,
and coils BX208 and BX211 form a series inductance LS2 253. This is
the partitioning of an auxiliary winding discussed previously
herein. The connection of inductances L2 252 and LS2 253 creates a
circuit node 254. A series circuit connection of capacitor CX2 255
and electronic AC switch SX 258 is connected from node 254 to
electrical terminal BX41 on coil BX211. A second capacitor CXO 256
is connected from electrical terminal BX11 on coil BX202 to BX41 on
coil BX211. Electronic AC switch SX 258 has a control input CN2 257
which is used in embodiments of the present invention to switch
capacitor CX2 255 into and out of control branch winding 251.
[0101] FIG. 2G is a circuit diagram of the inductance elements
(coils) CX203, CX206, CX209, and CX212 which make up auxiliary
branch winding BCX280, as described in FIG. 2C, wired to form
control branch winding 261 according to embodiments of the present
invention. Coils CX203 and CX206 form a series inductance L2 262,
and coils CX209 and CX212 form a series inductance LS2 263. This is
the partitioning of an auxiliary winding discussed previously. The
connection of inductances L2 262 and LS2 263 creates a circuit node
264. A series circuit connection of capacitor CX2 265 and
electronic AC switch SX 268 is connected from node 264 to
electrical terminal CX41 on coil CX212. A second capacitor CX0 266
is connected from electrical terminal CX11 on coil CX203 to CX41 on
coil CX212 Electronic AC switch SX 268 has a control input CN3 267
which is used in embodiments of the present invention to switch
capacitor CX3 265 into and out of control branch winding 261.
[0102] FIG. 2H is a circuit diagram illustrating a three phase
control winding 226 according to embodiments of the present
invention made by interconnecting branch control windings 241, 251
and 261 described in FIGS. 2E, 2F, and 2G respectively. Control
winding 226 is configured as a three phase Wye configured winding.
The electronic switches SX 248, 258 and 268 along with their
corresponding switched capacitors CX1 245, CX2 255 and CX3 265 are
designated as control elements 710, 720 and 730 respectively. While
the particular control elements are shown as having a
bi-directional electronic switch (e.g, SX 248, 258 and 268) for
connecting and disconnecting capacitors CX1 245, CX2 255 and CX3
265, a continuously electronically controllable capacitor would
still be within the scope of the present invention.
[0103] FIG. 2I is a circuit diagram of control winding 231 where
control elements 750, 760 and 770 are placed across a branch
control inductance LS2 252.
[0104] The control winding 231, in this example, is shown to have
the same branch elements as control winding 226. In this manner,
control elements 710, 720 and 730 may have the same values as when
used for control winding 226. Therefore, control winding 231 can be
used in a same manner as control winding 226. However, since the
capacitors (CX1 245, CX2 255 and CX3 265) are added with no
inductive isolation, more care would have to be taken to guarantee
that the capacitor terminal voltages are very near a zero value to
eliminate excessive transient currents. While this embodiment has a
more stringent switching requirement, switching the capacitors
within control winding 231 across only one inductive element (LS2
252) works and is within the scope of the present invention.
[0105] FIGS. 2J and 2K are circuit diagrams of another embodiment
of the present invention. In this embodiment, a control winding 240
is partitioned into two control windings 250 and 260. Control
winding 240 can be used in a same manner as control winding 226 or
231. Control windings 250 and 260 may be wound according to the
topology for control winding 226. For example branch winding
element L2 278 would be wound on the same stator teeth in the same
way as L21 238, however their respective electrical terminals would
be kept isolated creating two electrically independent but
magnetically coupled elements. In the same manner, branch winding
element LS2 277 and LS21 237 would be wound on the same stator
teeth again keeping their respective electrical terminals isolated.
Repeating this for all three of the three phase branch control
windings enables two magnetically coupled control windings that are
electrically isolated. Branch windings may be designed so that the
operation of a branch comprising L2 278 and LS2 277 and
corresponding capacitor C0 281 and a magnetically coupled branch
L21 238, LS21 237 and capacitor C00 291 is the same as
corresponding branch comprising L2 252, LS2 253 and CX0 256 of
control windings 226 (FIG. 2H) and 231 (FIG. 2I). If the
partitioned control winding 240 is made to be equivalent to control
winding 226 or control winding 231 in this manner on all three
branches, an extra level of control is possible allowing for a
finer control of added capacitance of a load range.
[0106] The embodiments of the present invention explained using
FIGS. 2A-2K illustrate using a three phase control winding to
control the outputs of two single phase energy windings. Using a
three phase control winding according to embodiments of the present
invention to control single phase outputs of a self-excited
induction generator is important in the generation of power in the
home market where single phase power is the primary power.
[0107] FIG. 2M is a circuit diagram illustrating an alternate
circuit configuration of the auxiliary control windings 226. In
FIG. 2M, the un-switched capacitors CX0 246, CX0 256, and CX0 266
are arranged in a Wye configuration. The basic control operation of
the circuit in FIG. 2M is the same as the description of the
configuration in FIG. 2H. The only difference may be in the actual
values of the capacitors CX0 246, CX0 256, and CX0 266 for a
particular set of branch windings comprising L1 242 and LS1 243, L2
252 and LS2 253, and L3 262 and LS3 263.
[0108] FIG. 2N is a circuit diagram illustrating another alternate
circuit configuration of the auxiliary control windings 226. In
FIG. 2N the un-switched capacitors CX0 246, CX0 256, and CX0 266
are arranged in a Delta configuration and the branch auxiliary
windings comprising L1 242 and LS1 243, L2 252 and LS2 253, and L3
262 and LS3 263 are also in a Delta configuration. The basic
control operation of the circuit in FIG. 2N is the same as the
description of the configuration in FIG. 2H.
[0109] FIG. 2P is a circuit diagram illustrating yet another
alternate circuit configuration of the auxiliary control windings
226. In FIG. 2P the un-switched capacitors CX0 246, CX0 256, and
CX0 266 are arranged in a Delta configuration and the branch
auxiliary windings comprising L1 242 and LS1 243, L2 252 and LS2
253, and L3 262 and LS3 263 are in a Wye configuration. The basic
control operation of the circuit in FIG. 2P is the same as the
description of the configuration in FIG. 2H. The only difference
may be in the actual values of the capacitors CX0 246, CX0 256, and
CX0 266 for a particular set of branch windings comprising L1 242
and LS1 243, L2 252 and LS2 253, and L3 262 and LS3 263.
[0110] The alternate circuit configurations FIG. 2M, FIG. 2N and
FIG. 2P for the auxiliary windings of FIG. 2H are included to
illustrate the varied ways that auxiliary control windings may be
configured and still be within the scope of embodiments of the
present invention. All the auxiliary control windings in FIGS.
1A-1L, FIGS.2A-2L, FIGS. 3A-3L, FIGS. 4A-4L, and FIGS. 6A-6L, may
be configured alternatively as was done in FIG. 2M, FIG. 2N and
FIG. 2P for the auxiliary control winding 226 in FIG. 2H as
additional embodiments of the present invention.
[0111] FIG. 3A is a cross-section of another induction machine 300
according to embodiments of the present invention. The stator 120,
rotor 117 and rotor windings 119 are given the same designators as
in FIGS. 1A and 2A. Since the teeth of the stator are wound
differently in this embodiment the teeth are given different
designators. Induction machine 300 has stator teeth 301-312. The
embodiment illustrated in FIG. 3A is configured to be wired with
two, two phase 2 pole energy windings (A, B, C) and (LA, LB, LC)
and one three phase auxiliary winding (AX, BX and CX). Energy coils
A302 and A308 are wound on stator teeth 302 and 308 respectively.
Energy coils B304 and B310 are wound on stator teeth 304 and 310.
Likewise, energy coils C306 and C312 are wound on stator teeth 306
and 312. Energy coils LA 301 and LA 307 are magnetically coupled
(wound on the same teeth) to auxiliary coils AX 301 and AX307
respectively. Energy coils LB 303 and LB 309 are magnetically
coupled (wound on the same teeth) to auxiliary coils BX 303 and
BX309 respectively. Likewise, energy coils LC 305 and LC 311 are
magnetically coupled (wound on the same teeth) to auxiliary coils
CX 305 and CX 311 respectively. The electrical terminals have the
same convention as used in FIGS. 1A and 2A.
[0112] FIG. 3B is a circuit diagram illustrating the connection of
the electrical terminals to create the branch windings for
induction generator 300. Energy coils A302 and A308 are coupled
with the electrical terminals sequence to create branch energy
winding BA330 and 2 magnetic poles in teeth 302 and 308. Energy
coils B304 and B310 are coupled with the electrical terminals
sequence to create branch energy winding BB335, and energy coils
C306 and C312 are coupled with the electrical terminal sequence to
create branch energy winding BB340. A second set of branch energy
windings, BLA345, BLB350 and BLC355 are created by coupling energy
coils LA301 and LA 307, LB303 and LB307, and LC305 and LC311,
respectively, with the shown electrical terminal sequences.
Referring to FIG. 3C, auxiliary branch winding BAX360 is created by
coupling auxiliary coils AX301 and AX307 with the electrical
terminal sequence shown. Auxiliary branch winding BBX365 is created
by coupling auxiliary coils BX303 and BX309 with the electrical
terminal sequence shown. Likewise, branch auxiliary winding BCX370
is created by coupling auxiliary coils CX305 and CX311 with the
electrical terminal sequence shown.
[0113] FIG. 3D is a circuit diagram illustrating an isolated three
phase Wye configured energy winding 328 of induction machine 300
created by coupling branch energy winding BA330, BB335 and BC340
with electrical terminals A21, B21 and C21 creating circuit node
327 and having electrical input or output terminals A11, B11 and
C11. Second three phase Wye configured energy winding 322 is
created by coupling branch energy windings BLA340, BLB345, and
BLC350 with their respective terminals A21, B21 and C21 creating
circuit node 323. Auxiliary three phase Wye configured winding 324
is magnetically coupled to energy winding 322 and is created by
connecting electrical terminals AX21, BX21 and CX21 of auxiliary
branch windings BAX360, BBX365 and BCX370 respectively.
[0114] FIG. 3E is a circuit diagram of the inductance elements
(coils) AX301 and AX307 which make up auxiliary branch winding
BAX360, as described in FIG. 3C, wired to form control branch
winding 341 according to embodiments of the present invention. Coil
AX301 forms an inductance L1 342 and coil AX307 forms an inductance
LS1 343. This is a partitioning of an auxiliary winding discussed
previously. The connection of L1 342 and LS1 343 creates a circuit
node 344. A series circuit connection of capacitor CX1 345 and
electronic AC switch SX 348 is connected from node 344 to
electrical terminal AX21 on coil AX307. A second capacitor CX0 346
is connected from electrical terminal AX11 on coil AX301 to
terminal AX21 on coil AX307. Electronic AC switch SX 348 has a
control input CN1 347 which is used in embodiments of the present
invention to switch capacitor CX1 345 into and out of control
branch winding 341.
[0115] FIG. 3F is a circuit diagram of the inductance elements
(coils) BX303 and BX309 which make up auxiliary branch winding
BBX365, as described in FIG. 3C, wired to form control branch
winding 351 according to embodiments of the present invention. Coil
BX303 forms an inductance L2 352 and coil BX309 forms an inductance
LS2 353. This is the partitioning of an auxiliary winding discussed
previously. The connection of L2 352 and LS2 353 creates a circuit
node 354. A series circuit connection of capacitor CX2 355 and
electronic AC switch SX 358 is connected from node 354 to
electrical terminal BX21 on coil BX309. A second capacitor CX0 356
is connected from electrical terminal BX11 on coil BX303 to
terminal BX21 on coil BX309. Electronic AC switch SX 358 has a
control input CN2 357 which is used in embodiments of the present
invention to switch capacitor CX2 355 into and out of control
branch winding 351.
[0116] FIG. 3G is a circuit diagram of the inductance elements
(coils) CX305 and CX311 which make up auxiliary branch winding
BCX365, as described in FIG. 3C, wired to form control branch
winding 361 according to embodiments of the present invention. Coil
CX305 forms an inductance L3 362 and coil CX311 forms an inductance
LS3 363. This is the partitioning of an auxiliary winding discussed
previously. The connection of inductances L3 362 and LS3 363
creates a circuit node 364. A series circuit connection of a
capacitor CX3 365 and an electronic AC switch SX 368 are connected
from node 364 to electrical terminal CX21 on coil CX311. A second
capacitor CX0 366 is connected from electrical terminal CX11 on
coil CX305 to terminal CX21 on coil CX311. Electronic AC switch SX
368 has a control input CN3 367 which is used in embodiments of the
present invention to switch capacitor CX3 365 into and out of
control branch winding 361.
[0117] FIG. 3H is a circuit diagram illustrating a three phase
control winding 326 according to embodiments of the present
invention made by interconnecting branch control windings 341, 351
and 361 described in FIGS. 3E, 3F, and 3G respectively. Control
winding 326 is configured as a three phase We winding. The
electronic switches SX 348, 358 and 368 along with their
corresponding switched capacitors CX1 345, CX2 355 and CX3 365 are
designated as control elements 715, 725 and 735 respectively. While
the particular control elements are shown as having a
bi-directional electronic switch (e.g., SX 348, 358 and 368) for
connecting and disconnecting capacitors CX1 345, CX2 355 and CX3
365 respectively, a continuously electronically controllable
capacitor would still be within the scope of the present
invention.
[0118] FIG. 3I is a circuit diagram of control winding 331 where
control elements 715, 725 and 735 are placed across a branch
control inductance LS2 353. The control winding 331, in this
example, is shown to have the same branch elements as control
winding 326. In this manner, control elements 715, 725 and 735 may
have the same values as when used for control winding 326.
Therefore, control winding 331 can be used in a same manner as
control winding 326. However, since the capacitors (CX1 345, CX2
355 and CX3 365 in control elements 715, 725 and 735 respectively)
are added with no inductive isolation, more care would have to be
taken to guarantee that the capacitor terminal voltages are very
near a zero value to eliminate excessive transient currents. While
this embodiment has a more stringent switching requirement,
switching the capacitors within control winding 331 across only one
inductive element (LS2 353) works and is within the scope of the
present invention.
[0119] FIGS. 3J and 3K are circuit diagrams of another embodiment
of the present invention. In this embodiment, a control winding 340
is partitioned into two control windings 350 and 360. Control
winding 340 can be used in a same manner as control windings 326 or
331. Control windings 350 and 360 may be wound according to the
topology for control winding 326. For example, branch winding
element L2 378 would be wound on the same stator teeth in the same
way as L21 338, however their respective electrical terminals would
be kept isolated creating two electrically independent but
magnetically coupled elements. In the same manner, branch winding
elements LS2 377 and LS21 337 would be would on the same stator
teeth again keeping their respective electrical terminals isolated.
Repeating this for all three of the three phase branch control
windings enables two magnetically coupled control windings that are
electrically isolated. Branch windings may be designed so that the
operation of a branch comprising L2 378 and LS2 377 and
corresponding capacitor C0 381 and a magnetically coupled branch
L21 338, LS21 337 and capacitor C00 391 is the same as a
corresponding branch comprising L2 352, LS2 353 and CX0 356 of
control winding 331 (FIG. 3I) and control winding 326 (FIG. 3H). If
the partitioned control winding 340 is made to be equivalent to
control windings 326 or 331 in this manner on all three branches,
an extra level of control is possible allowing for a finer control
of added capacitance of a load range.
[0120] FIG. 4A is a cross-section of another induction machine 400
according to embodiments of the present invention. The stator 120,
rotor 117 and rotor windings 119 are given the same designators.
Since the teeth of the stator are wound differently in this
embodiment, the teeth are given different designators. Induction
machine 400 is wound as having two single phase windings (L and A)
and one three phase (AX, BX and CX) auxiliary winding. Induction
machine 400 has stator teeth 401-412. Coils L401, L402, L403, L407,
L408, and L409 are wound on teeth 401, 402, 403, 407, 408 and 409
respectively to produce two magnetic poles (North and a South).
Likewise, coils A404, A405, A406, A410, A411, and A412 are wound on
teeth 404, 405, 406, 410, 411, and 412 respectively to create two
magnetic poles (North and a South). Auxiliary coils AX401 and AX407
are wound on teeth 401 and 407, auxiliary coils BX402 and BX408 are
wound on teeth 402 and 408, and auxiliary coils CX403 and CX409 are
wound on teeth 403 and 409 to each create 2 magnetic poles (North
and South). The electrical terminal designations follow the same
convention as described in FIG. 2A.
[0121] FIG. 4B is a circuit diagram illustrating how the individual
coils are connected and the magnetic couplings for the induction
machine 400. The coils L401, L402, L403, L407, L408, and L409 are
connected in their electrical terminal sequence shown in FIG. 4B to
create a two pole single phase energy winding BL303. Likewise, a
second two pole single phase energy winding BA304 is created by
connecting the electrical terminals of the energy coils A404, A405,
A406, A410, A411 and A412 in the sequence shown. Auxiliary coils
AX401, BX402, CX403, AX407, BX408, and CX409 are magnetically
coupled (wound on the same stator tooth) to energy coils L401,
L402, L403, L407, L408, and L409 respectively. Auxiliary coils
AX401, BX402, CX403, AX407, BX408, and CX409 are connected with the
electrical terminal sequence shown to create three branch auxiliary
windings with electrical terminals AX11, BX11, CX11, AX21, BX21,
and CX21.
[0122] FIG. 4C is a circuit diagram of the branch windings
introduced in FIG. 4B. Auxiliary coils AX401 and AX407 are coupled
to form branch auxiliary winding BAX460. Auxiliary coils BX402 and
BX408 are coupled to form auxiliary branch winding BBX470.
Likewise, auxiliary coils CX403 and CX409 are coupled to branch
auxiliary winding BCX480.
[0123] FIG. 4D is a circuit diagram of single phase energy winding
BA304 and single phase energy winding BL303 which is magnetically
coupled (422) to three phase We configured auxiliary winding 424.
Three phase auxiliary winding 424 is created by connecting
electrical terminals AX21, BX21, and CX21 of branch auxiliary
windings BAX460, BBX470 and BCX480, respectively, creating circuit
node 425. Three phase auxiliary winding 424 has terminals AX11,
BX11 and CX11. Energy winding BL303 has input or output terminals
L11 and L61, while energy winding BA304 has input or output
terminals A11 and A61. Note that energy windings BA304 and BL303
are magnetically and electrically isolated. Magnetic coupling of
energy windings BA304 and BL303 only occurs due to their rotational
interaction with rotor 117.
[0124] FIG. 4E is a circuit diagram of the inductance elements
(coils) AX401 and AX407 which make up auxiliary branch winding
BAX460, as described in FIG. 4C, wired to form control branch
winding 441 according to embodiments of the present invention. Coil
AX401 forms an inductance L1 442 and coil AX407 forms an inductance
LS1 443. This is a partitioning of an auxiliary winding discussed
previously herein. The connection of inductances L1 442 and LS1 443
creates a circuit node 444. A series circuit connection of
capacitor CX1 445 and electronic AC switch SX 448 is are connected
from node 444 to electrical terminal AX21 on coil AX407. A second
capacitor CX0 446 is connected from electrical terminal AX11 on
coil AX401 to terminal AX21 on coil AX407. Electronic AC switch SX
448 has a control input CN1 447 which is used in embodiments of the
present invention to switch capacitor CX1 445 into and out of
control branch winding 441.
[0125] FIG. 4F is a circuit diagram of the inductance elements
(coils) BX402 and BX408 which make up auxiliary branch winding
BBX470, as described in FIG. 4C, wired to form control branch
winding 451 according to embodiments of the present invention. Coil
BX402 forms an inductance L2 452 and coil BX408 forms an inductance
LS2 453. This is the partitioning of an auxiliary winding discussed
previously herein. The connection of inductances L2 452 and LS2 453
creates a circuit node 454. A series circuit connection of
capacitor CX2 455 and electronic AC switch SX 458 are connected
from node 454 to electrical terminal BX21 on coil BX408. A second
capacitor CX0 456 is connected from electrical terminal BX11 on
coil BX402 to terminal BX21 on coil BX408. Electronic AC switch SX
458 has a control input CN2 457 which is used in embodiments of the
present invention to switch capacitor CX2 455 into and out of
control branch winding 451.
[0126] FIG. 4G is a circuit diagram of the inductance elements
(coils) CX403 and CX409 which make up auxiliary branch winding
BCX480, as described in FIG. 4C, wired to form control branch
winding 461 according to embodiments of the present invention. Coil
CX403 forms an inductance L3 462 and coil CX409 forms an inductance
LS3 463. This is the partitioning of an auxiliary winding discussed
previously. The connection of inductances L3 462 and LS3 463
creates a circuit node 464. A series circuit connection of
capacitor CX3 465 and electronic AC switch SX 468 is connected from
node 464 to electrical terminal CX21 on coil CX409. A second
capacitor CX0 466 is connected from electrical terminal CX11 on
coil CX403 to CX21 on coil CX409. Electronic AC switch SX 468 has a
control input CN3 467 which is used in embodiments of the present
invention to switch capacitor CX3 465 into and out of control
branch winding 461.
[0127] FIG. 4H is a circuit diagram illustrating a three phase
control winding 426 according to embodiments of the present
invention made by interconnecting branch control windings 441, 451
and 461 described in FIGS. 4E, 4F, and 4G respectively. Control
winding 426 is configured as a three phase We winding. The
electronic switches SX 448, 458 and 468 along with their
corresponding switched capacitors CX1 445, CX2 455 and CX3 465 are
designated as control elements 775, 790 and 795 respectively. While
the particular control elements are shown as having a
bi-directional electronic switch (e.g., SX 448, 458 and 468) for
connecting and disconnecting capacitors CX1 445, CX2 455 and CX3
465, a continuously electronically controllable capacitor would
still be within the scope of the present invention.
[0128] FIG. 4I is a circuit diagram of control winding 431 where
control elements 775, 790 and 795 are placed across a branch
control inductance LS2 453. The control winding 431, in this
example, is shown to have the same branch elements as control
winding 426. Therefore, control winding 431 can be used in a same
manner as control winding 426. In this manner, control elements
775, 790 and 795 may have the same values as when used for control
winding 426. However, since the capacitors (CX1 445, CX2 455 and
CX3 465 in control elements 775, 790 and 795 respectively) are
added with no inductive isolation, more care would have to be taken
to guarantee that the capacitor terminal voltages are very near a
zero value to eliminate excessive transient currents. While this
embodiment has a more stringent switching requirement, switching
the capacitors within control winding 431 across only one inductive
element (LS2 453) works and is within the scope of the present
invention.
[0129] FIGS. 4J and 4K are circuit diagrams of another embodiment
of the present invention. In this embodiment, a control winding 440
is partitioned into two control windings 450 and 460. Control
winding 440 can be used in a same manner as control windings 426 or
431. Control windings 450 and 460, in this embodiment, may be wound
according to the topology for control winding 426. For example
branch winding element L2 478 would be wound on the same stator
teeth in the same way as L21 438, however their respective
electrical terminals would be kept isolated creating two
electrically independent but magnetically coupled elements. In the
same manner, branch winding element LS2 477 and LS21 437 would be
wound on the same stator teeth again keeping their respective
electrical terminals isolated. Repeating this for all three of the
three phase branch control windings enables two magnetically
coupled control windings that are electrically isolated. Branch
windings may be designed so that the operation of a branch
comprising L2 478 and LS21 477 and corresponding capacitor C0 481
and a magnetically coupled branch L21 438, LS21 437 and capacitor
C00 491 is the same as the corresponding branch comprising L2 452,
LS2 453 and CX0 456 (see FIGS. 4H and 4I). If the partitioned
control winding 440 is made to be equivalent to control winding 426
in this manner on all three branches, an extra level of control is
possible allowing for a finer control of added capacitance of a
load range.
[0130] FIG. 6A is a cross-section of an induction machine 600.
Induction machine 600 has a stator 6120 with "teeth" 601-624 on
which corresponding energy coils, A601, A607, A613, A619, B603,
B609, B615, B621, C605, C611, C617, C623 and auxiliary coils AX602,
AX608, AX614, AX620, BX604, BX610, BX616, BX622, CX606, CX612,
CX618, CX624 are wound. Rotor 6117 is rotatable disposed within and
on the center axis of the stator 6120 and rotates on shaft 6118.
Rotor 6117 has coils (e.g., 6119) wound in slots on its outer
surface. Magnetic flux lines (e.g., like 501) couple to the rotor
6117 and thus to rotor coils through the circumferential air gap
6100 between the rotor 6117 and stator 6120. Rotor coils, like
exemplary coils 6119, are typically shorted loops which create a
"squirrel cage" rotor design. Induction machine 600 is configured
so that the energy and auxiliary coils may be wound to form a 4
pole three phase energy winding and a 4 pole three phase auxiliary
winding where the energy winding and the auxiliary winding are
magnetically and electrically isolated.
[0131] FIG. 6B is a circuit diagram of the connection sequence for
the coils (e.g., A601, A607, A613, A619) on stator teeth 601-624.
The particular electrical connection of the terminals, A12 to A22
and A21 to A31 and A32 to A42, for coils A601, A607, A613, A619,
creates a North magnetic pole at teeth 601 and 619 and a South
magnetic pole at teeth 607 and 613 for a current flow into terminal
A11 and out of terminal A41. The connection of coils A601, A607,
A613, A619 creates a branch energy winding BA630. A same connection
sequence for coils B603, B609, B615, B621 (B12 to B22 and B21 to
B31 and B32 to B42) creates branch energy winding BB640. For a
current flow into terminal B11 and out of terminal B41, branch
winding BB640 creates a North magnetic pole at teeth 603 and 621
and a South magnetic pole at teeth 609 and 615. Likewise, a same
connection sequence for coils C605, C611, C617, C623 (C12 to C22
and C21 to C31 and C32 to C42) creates branch energy winding BC650.
For a current flow into terminal C11 and out of terminal C41,
branch energy winding BC650 creates a North magnetic pole at teeth
605 and 623 and a South magnetic pole at teeth 611 and 617.
[0132] FIG. 6C is a circuit diagram of the connection sequence for
the auxiliary coils AX602, AX608, AX614, AX620 to create auxiliary
branch winding BAX660, auxiliary coils BX604, BX610, BX616, BX622
to create auxiliary branch winding BBX670, and auxiliary coils
CX606, CX612, CX618, CX624 to create auxiliary branch winding
BCX680. The circuit diagrams in FIG. 6B and FIG. 6C illustrate the
symmetrical wiring employed in winding induction machines used in
embodiments of the present invention. It should be noted that the
branch windings (BAX660, BBX670 and BCX680) are a series connection
of individual inductances whose interconnection points may form
intermediate nodes that may be wired to additional circuit
elements. For example, the connection node of exemplary terminals
A12 and A22 may have their connection wired so that additional
external components may be used. Embodiments of the present
invention use the partitioning of the auxiliary branch windings
BAX660, BBX670 and BCX680 to create a control winding for induction
generator configurations.
[0133] FIG. 6D is a circuit diagram that illustrates the magnetic
and electrical structure created when branch energy windings BA630,
BB640 and BC650 are configured as a We three phase energy winding
626 by connecting terminals A41, B41 and C41 creating a node 627,
and branch auxiliary windings BAX660, BBX670 and BCX680 are
configured as a We three phase winding 628 by connecting terminals
AX41, BX41 and CX41 creating node 629. Nodes 627 and 629 are
electrically neutral potential points with respect to the three
phase windings 626 and 628, respectively, and may be used in
embodiments of the present invention as a ground or reference
point. Electrical terminals A11, C11 and B11 and node 627 may be
wired to external inputs or outputs (not shown). Likewise,
electrical terminals AX11, CX11 and BX11 and node 629 may be wired
to external circuits to create a control winding according to
embodiments of the present invention.
[0134] FIG. 6E is a circuit diagram of the inductance elements
(coils) AX602, AX608, AX614, and AX620 which make up auxiliary
branch winding BAX660, as described in FIG. 6C, wired to form
control branch winding 641 according to embodiments of the present
invention. Coils AX602 and AX608 form a series inductance L1 642,
and coils AX614 and AX620 form a series inductance LS1 643. This is
the partitioning of an auxiliary winding discussed previously
herein. The connection of inductances L1 642, and LS1 643 creates a
circuit node 644. A series circuit connection of capacitor CX1 645
and electronic AC switch SX 648 is connected from node 644 to
electrical terminal AX41 on coil AX620. A second capacitor CX0 646
is connected from electrical terminal AX11 on coil AX602 to AX41 on
coil AX620. Electronic AC switch SX 648 has a control input CN1 647
which is used in embodiments of the present invention to switch
capacitor CX1 645 into and out of control branch winding 641.
[0135] FIG. 6F is a circuit diagram of the inductance elements
(coils) BX604, BX610, BX616, and BX622 which make up auxiliary
branch winding BBX670, as described in FIG. 6C, wired to form
control branch winding 651 according to embodiments of the present
invention. Coils BX604 and BX610 form a series inductance L2 652,
and coils BX616 and BX622 form a series inductance LS2 653. This is
the partitioning of an auxiliary winding discussed previously. The
connection of inductances L2 652 and LS2 653 creates a circuit node
654. A series circuit connection of capacitor CX2 655 and
electronic AC switch SX 658 is connected from node 654 to
electrical terminal BX41 on coil BX622. A second capacitor CX0 656
is connected from electrical terminal BX11 on coil BX604 to BX41 on
coil BX622. Electronic AC switch SX 658 has a control input CN2 657
which is used in embodiments of the present invention to switch
capacitor CX2 655 into and out of control branch winding 651.
[0136] FIG. 6G is a circuit diagram of the inductance elements
(coils) CX606, CX612, CX618, and CX624 which make up auxiliary
branch winding BCX680, as described in FIG. 6C, wired to form
control branch winding 661 according to embodiments of the present
invention. Coils CX606 and CX612 form a series inductance L3 662,
and coils CX618 and CX624 form a series inductance LS2 663. This is
the partitioning of an auxiliary winding discussed previously. The
connection of inductances L3 662 and LS3 663 creates a circuit node
664. A series circuit connection of capacitor CX3 665 and
electronic AC switch SX 668 is connected from node 664 to
electrical terminal CX41 on coil CX624. A second capacitor CX0 666
is connected from electrical terminal CX11 on coil CX606 to CX41 on
coil CX624. Electronic AC switch SX 668 has a control input CN3 667
which is used in embodiments of the present invention to switch
capacitor CX3 665 into and out of control branch winding 661.
[0137] FIG. 6H is a circuit diagram illustrating a three phase
control winding 649 according to embodiments of the present
invention made by interconnecting branch control windings 641, 651
and 661 described in FIGS. 6E, 6F, and 6G respectively. Control
winding 649 is configured as a three phase We winding. The
electronic switches SX 648, 658 and 668 along with their
corresponding switched capacitors CXI 645, CX2 655 and CX3 665 are
designated as control elements 740, 745 and 755 respectively. While
the particular control elements are shown as having a
bi-directional electronic switch (SX 648, 658 and 668) for
connecting and disconnecting capacitors CX1 645, CX2, 655 and CX3
665 a continuously electronically controllable capacitor would
still be within the scope of the present invention.
[0138] FIG. 6I is a circuit diagram of a control winding 631 where
control elements 740, 745 and 755 are placed across a branch
control inductance LS2 653. The control winding 631, in this
example, is shown to have the same branch elements as control
winding 649. Therefore, control winding 631 can be used in a same
manner as control winding 649. In this manner control elements 740,
745 and 755 may have the same component values as when used for
control winding 649. However, since the capacitors CX1 645, CX2 655
and CX3 665 are added with no inductive isolation, more care would
have to be taken to guarantee that the capacitor terminal voltages
were very near a zero value to eliminate excessive transient
currents. While this embodiment has a more stringent switching
requirement, switching the capacitors within control winding 631
across only one inductive element (LS2 653) works and is within the
scope of the present invention.
[0139] FIGS. 6J and 6K are circuit diagrams of another embodiment
of the present invention. In this embodiment, a control winding 640
is partitioned into two control windings 650 and 660. Control
winding 640 can be used in a same manner as control windings 649 or
631. Control windings 650 and 660 may be wound according to the
topology for control winding 649. For example, branch winding
element L2 678 would be wound on the same stator teeth in the same
way as L21 638, however their respective electrical terminals would
be kept isolated creating two electrically independent but
magnetically coupled elements. In the same manner, branch winding
element LS2 677 and LS21 637 would be wound on the same stator
teeth again keeping their respective electrical terminals isolated.
Repeating this for all three of the three phase branch control
windings enables two magnetically coupled control windings that are
electrically isolated.
[0140] Branch windings may be designed so that the operation of a
branch comprising L2 678 and LS2 677 and corresponding capacitor C0
681 and a magnetically coupled branch L21 638, LS21 637 and
capacitor C00 691 is the same as a corresponding branch comprising
L2 652, LS2 653 and CX0 656 in branch control winding 649 of FIG.
6H. If the partitioned control winding 640 is made to be equivalent
to control winding 649 in this manner on all three branches, an
extra level of control is possible allowing for a finer control of
added capacitance of a load range.
[0141] FIG. 7A is a block diagram of an induction generating system
780 employing a stand-alone self-excited induction generator 782,
according to embodiments of the present invention, driving a
variable electrical load 785. Self-excited induction generator 782
may employ any of the compatible auxiliary control windings and
energy windings described in the embodiments of FIGS. 1A-1L, 2A-2L,
3A-3L, 4A-4L and 6A-6L for auxiliary (AUX) windings 791 and three
phase energy windings 798. The particular embodiment for energy
windings 798 would depend on whether single phase or three phase
energy windings were desired.
[0142] Load switch 830 may engage to connect load 785 in response
to conditions of outputs 786 or in response to an optional signal
897 from master controller 893. In FIG. 7A and in the other systems
illustrated in FIGS. 7B, 8, 9, 10, and 11, master controller 893
and the signals (892 and 897) coupled to it from an engine
controller (e.g., 783), a generator controller (e.g., 784) and a
load switch (e.g., 830) may have the same designators for
simplicity of the figures.
[0143] Master controller 893 sends and receives user signals 918
from a user interface (not shown). The signals establish the mode
of operation for a system 780. Master controller 893 also receives
engine status from signals 799 via engine controller 783, engine
control and status signals 891, and induction generator 782 status
from generator controller 784 via signals 892. Generator controller
784 also receives signals, load voltage 788 and load current 787,
from load 785. Parameters of load voltage 788 and load current 787
(may include amplitude, phase, rate of change of voltage, rate of
change of current, etc.). Master controller 893 may send signals to
engine controller 783 indicating a desired engine speed,
revolutions per minute (RPM) and engine controller 783 may exercise
algorithms along with control signals 799 to cause ignition and
throttle electrical and electromechanical devices to start and
accelerate engine 781. Generator controller 784 would receive load
voltage 788 and load current 787 signals and determine the
capacitance needed in auxiliary windings 791 according to
embodiments of the present invention and generate control signals
that switch in appropriate capacitor (e.g., CX1 245, CX2 255 and
CX3 265) combinations using control elements (e.g., 750, 760, and
770) to optimize auxiliary windings 791 for induction generator
782.
[0144] A prime mover engine 781 is used to supply rotational
mechanical energy to induction generator 782 via a shaft 789. The
induction generator 782 has three phase outputs 786, however other
combinations of phase outputs (1 or 2 phase) are possible without
departing from the scope of the present invention. Induction
generator 782 employs a single energy winding that may be
configured either as a three phase Wye or Delta circuit. Likewise,
induction generator 782 may employ one or more auxiliary control
windings as described in the embodiments of FIGS. 1K-1L, 2K-2L,
3K-3L, 4K-4L, 6K-6L. Feedback signals load voltage 786 and load
current 787 represent the currents and voltages of phases 786
driving variable electrical load 785. Signals 787 and 788 are
coupled to controller 784. Controller 784 couples signals to switch
elements (e.g., 248, 258 and 268) via control inputs (e.g., CN1
247, CN2 257 and CN3 267) to control the auxiliary windings of
induction generator 782 in response to changes that occur in
variable load 785. Since controller 784 is electrical, it may
operate on each electrical cycle of phase outputs 786. The engine
control 783 is electromechanical and is slower to respond to
changes in the voltage and current outputs (e.g., frequency,
amplitude, phase, etc.) of induction generator 782. Depending on
the characteristics of the variable electrical load 785, there are
theoretical optimum capacitance values coupled to the auxiliary
windings of induction generator 782 and control settings for engine
781. Induction generator 782 may be configured as described in FIGS
1A-1L, 3A-3L, and 6A-6L. Each of these configurations has a three
phase energy winding and a three phase auxiliary winding.
[0145] A typical operation of the embodiment in FIG. 7A may be as
follows:
[0146] Engine 781 is coupled to induction generator 782 with shaft
789. If the rotor of induction generator 782 has some residual
magnetism, then simply starting engine 781 and bringing it up to
speed will start the process of establishing flux by induction in
auxiliary windings 791. Embodiments of the present invention may
use circuits in controller 784 to "pulse" the auxiliary windings
with energy to start the excitation of auxiliary winding 791 if the
voltages on auxiliary winding 791 do not establish once induction
generator 782 rotation has commenced. For a particular design of
induction generator 782, there will be a rotation speed for engine
781 necessary to determine the correct and desired frequency of the
output on energy windings 786. Load switch 830 may keep the
variable load 785 disconnected until induction generator 782 is
brought up to an initial speed. Engine 781 may be started in a no
load condition where variable load 785 is disconnected via load
switch 830. Controller 784 may be designed to only begin
controlling after the engine speed is within a range of its steady
state value using an engine speed sense signal in signals 797.
After the engine speed has stabilized, controller 784 would sense
the current supplied to the load 785 and continually adjust the
amount of auxiliary winding capacitance as a function of the load
current 787 and load voltage 788. If one did not have a control
winding corresponding to embodiments of the present invention, the
induction generator may have to be sized so that the output voltage
could be maintained strictly by controlling the speed of the engine
784 and a user may have to accept poor quality outputs 786 without
optimization of auxiliary windings 791. Changing the capacitance on
the auxiliary winding 791, according to embodiments of the present
invention, optimizes the capacitance for a load 785 as it varies
and thus the engine 781 is required to maintain a condition
proportional to an optimized generator. Since the controller 784
electronically switches the capacitance quickly as the load
changes, it optimizes the auxiliary (field) windings 791 so the
engine 781 only has to change its speed based on a power
requirement for a higher efficiency generator. The generator
control loop, from outputs 786 through controller 784 (signals 788
and 787) and auxiliary windings 791 is a fast control loop, and the
engine control loop from engine controller 783 to engine 781 is a
slower control loop. The rotational inertia of the mechanical
system ensures that the fast control loop can respond to a change
in current and optimize the generator 782 for a changing load 785
before the engine 781 either has to speed up or slow down to
maintain the voltage for the changed load power requirement. The
engine controller 783 would receive a new RPM set point, in one
embodiment of the present invention, based on changing conditions
of the load 785 determined by analyzing load voltage 788 and load
current 787 via generator controller 784 and master controller 893.
This is further described with respect to FIGS. 15 and 16.
Generator 782 may also have a single phase output (single phase
output 786) (e.g., embodiments of FIGS. 2A-2L and FIGS. 4A-4L)
without departing from the scope of the system embodiment in FIG.
7A.
[0147] As described previously, embodiments of the present
invention use electronic AC switches (e.g., triac 128) to switch
discrete capacitors in and out of portions of auxiliary windings
791. In these embodiments, capacitance is added or removed in
discrete amounts and controller 784 would comprise a combination of
digital and analog circuitry. The analog circuits would comprise
circuits used to sense parameters of the load voltage 788 and load
current 787. The digital circuits would process digitized versions
of these analog signals to generate control signals (e.g., CN1 147,
CN2 157, and CN3 167 in FIG. 1H) for control elements (e.g.,
control elements 750, 760 and 770 in FIG. 1H) of auxiliary control
windings 791. A desired set point speed engine 781 would be
calculated based on parameters of signals 788 and 787 and passed to
engine controller 783 via signals 892 and 891 via master controller
893 or directly via signal 797.
[0148] FIG. 7B is a block diagram of another induction system 700
employing an induction generator 734 according to embodiments of
the present invention. A power grid 732 supplies three phase lines
731 to energy windings 733 (configured as a three phase Wye or
Delta circuit) in induction generator 734. The three phase rotating
magnetic field produced by energy windings 733 cause the rotor of
induction generator 734 to rotate (by induction) as an induction
motor. Energy stored in the rotor windings of induction generator
734 are transferred to second energy winding 736 coupled with three
phase outputs 737 to variable electrical load 738. The
configuration in FIG. 7B operates as a power conditioner where the
power grid 732 sets the frequency of the outputs 737, and the
induction generator 734 and associated controls would determine the
output voltage quality. Feedback signals, parameters of load
voltage 739 and load current 792, are used to control auxiliary
windings 741 via a controller 793 according to embodiments of the
present invention. Controller 793 would generate signals used as
control inputs (e.g., CN1 502, CN2 510 and CN3 512) to auxiliary
windings 741 to optimize the outputs 737 in response to changes in
the characteristics of variable electrical load 738. In this
embodiment, a function of the auxiliary winding 741 and the
controller 793 is to monitor and control the power factor of the
energy delivered to variable electrical load 738 via outputs 737.
Master controller 893 sends mode information to controller 793 and
may send a control signals 897 to switches 830. 821 and 822 which
determine the power flow within induction system 700. In one mode,
switch 821 connects the power grid 732 to energy winding 733 and
load switch 830 disconnects energy winding from the load 738.
Switch 822 connects the power grid to the load 738. Induction
generator 734 is powered by power grid 732 and begins to rotate.
Controller 793 monitors the output voltage and determines the speed
of induction generator 734. When induction generator 734 is at the
proper speed switch 822 is opened and load switch 830 connects the
output of induction generator 734 to load 738. Controller 793
monitors the parameters of the load voltage 739 and current 792 and
switches capacitance within auxiliary windings 741 to control the
voltage levels and power factor at load 738. The output of
induction generator 734 is frequency locked to power grid 732,
however the load power is isolated and conditioned by induction
generator 734 by the action of the control to auxiliary windings
741 according to embodiments of the present invention.
[0149] FIG. 7C is a block diagram of another system embodiment of
the present invention. In this embodiment, AC power grid 857 is
coupled via lines 858 and switch 871 (either inputs or outputs) via
an optional switch 823 to a single energy winding 854 in induction
generator 856 and to a variable electrical load 860 via load switch
830. (Note, throughout the various embodiments of the present
invention, such load switches may operate in an automatic fashion
dependent only upon the level of signals on the load lines. Switch
821 is used to disconnect the AC power grid 857 in case of a
failure. Control signal 863 may be generated by circuitry in
controller 855 by determining a failure (loss of voltage or
excessive load current) of AC power grid 857.
[0150] In one mode of this embodiment, auxiliary windings 867 and
controller 855 are used to control the power factor of the variable
electrical load 860 as induction generator 856 is operated over its
range of a net receiver of power to a net deliverer of power (to
the AC power grid 857 and the load 860). In this embodiment, the AC
power grid 857 provides the excitation for the field of induction
generator 856. Depending on the speed of engine 865 coupled to
induction generator 856 with shaft 866, induction generator 856 may
provide energy to both load 860 and back to AC power grid 857.
Master controller 893 may determine the requirement for the
generator 856 to supply energy to AC power grid 857 and send
corresponding speed requirements to engine controller 861 via
signals 891. Signals 891 would also feed back to master controller
893 parameters of engine 865 (e.g., engine speed). Master
controller 893 would also couple signals 892 to controller 855.
Controller 855 would control the capacitance on auxiliary windings
867 based on parameters of load voltage 862 and load current 865
and signals from master controller 893. Load switch 830 may simply
monitor the inputs 859 and determine when to connect load 860 or
master controller 893 may control load switch 830 with control
lines 897.
[0151] In a second mode of operation for system 850, AC power grid
857 may be disconnected from energy winding 854 by switch 821 by
control signals 897. In this embodiment, controller 855 would
control the capacitance auxiliary windings 867 to provide a
self-excited induction generator 856. The amount of capacitance in
auxiliary winding would be selected in response to parameters of
load voltage 862 and load current 865 signals. Master controller
893 receives user inputs 918 and sets speed set points to engine
controller 861 via signals 891. Engine controller 861 controls the
speed of engine 865 based set points received from master
controller 918 which determines the required engine 865 speed in
response to load conditions determined from signals load voltage
862 and load current 865. In the system 850 illustrated in FIG. 7C,
the generator 856 may alternate from a line excited generator with
the auxiliary winding 867 and controller 855 controlling load power
factor and the quality of outputs 859 to a self-excited induction
generator where the auxiliary windings 867 and controller 855
controls the auxiliary capacitance to optimize generator as load
860 varies in response to parameters of signals load voltage 862
and load current 865.
[0152] If induction system 850 has optional switch 823, then
additional modes are possible. In the first mode, switch 823 is OFF
and switches 821 and 830 are ON and the power grid 857 drives load
860 directly. Engine 865 may then be started by conventional means
and controller 855 determines when induction generator 856 is up to
a desired speed. Switch 823 may be then switch ON and the energy
flow is determined by the operational speed of Engine 865. In
another mode, switch 823 is ON and power grid 857 causes induction
generator 856 to rotate which in turn rotates Engine 865 to enable
it to start. Upon Engine 865 starting, switch 823 is turned OFF by
control signals 897 until induction generator 856 achieves a
desired speed.
[0153] In a second mode switch 821 is OFF and Engine 865 drives
induction generator 856 via shaft 866. Switches 823 and 830 are ON
and energy winding 854 supplies load 860. Controller 855 monitors
load voltage 862 and load current 865 and adjust the capacitors on
auxiliary windings 867 to control the output voltage and power
factor of the energy delivered to load 860. Engine controller 861
receives signals 797 to control Engine 865 to a desired speed
dependent on user inputs 918 and variations in the load 860.
[0154] In a third mode, switches 821, 823 and 830 are all ON and
control of Engine 865 determines the net flow of energy from
induction generator 856. Induction generator 856 either supplies
energy to the power grid 857 and load 860 or operates as a load
conditioner. In either case, controller 855 controls the capacitors
on 5 auxiliary windings 867 to control voltage and power factor on
load 860 according to embodiments of the present invention.
[0155] FIG. 7D is a block diagram of an induction system 2001 which
is the similar to the induction system 780 in FIG. 7A. Induction
generator 2002 has three phase energy/control windings 2000 and no
auxiliary control windings like auxiliary control windings 791
within induction generator 782 of system 780 . In this embodiment
of the present invention, the energy/control windings 2000 provide
the field excitation the same way as auxiliary windings 791 for
induction generator 782 in system 780. The operation and control of
system 2001 are very similar to system 780, the primary difference
is that the combination energy/control windings 2000 may be a
design compromise over the separate energy windings 798 and
auxiliary windings 791 of system 780. In the system 2001 the
energy/control windings 2001 have to be designed for the load they
are required to drive and this may require the capacitors to have a
higher voltage rating and also to have larger capacitance values.
The embodiment of the present invention in FIG. 7D has the same
control methodology as the embodiment in FIG. 7A. Any of the
systems in FIGS. 7B, 7C, 8, and 9 may be correspondingly modified
like system 2001 in FIG. 7D to allow operation with combination
energy/control windings and still be within the scope of
embodiments of the present invention.
[0156] FIG. 8 is another induction system 800 employing an
induction generator 806 according to embodiments of the present
invention. AC power grid 807 has three phase lines 808 (either
inputs or outputs) coupled to energy windings 803 via switch 821.
Induction generator 806 is coupled to a variable electrical load
810 via load switch 830 with three phase energy windings 804 which
generate outputs 809. Induction generator 800 also has auxiliary
windings 817 configured according to embodiments of the present
invention and controlled by controller 805. Controller 805 receives
feedback signals load voltage 812 and load current 815 from
variable electrical load 810. An engine 818 is coupled to induction
generator 806 via a shaft 816 and is operable to supply rotational
mechanical energy. Engine 818 is controlled by engine controller
811 which is coupled to master controller 893 with signals 891.
Master controller 893 sends mode information and receives signals
from controller 805 via signals 892. Master controller 893 also
receives user inputs 918. Induction generator 806 also has an
inertial energy storage element (e. g., flywheel) 814. Engine
controller 811 operates according to the description of the engine
controller in FIG. 11.
[0157] The induction system 800 employs an induction generator 806
which has two electrically and magnetically isolated energy
windings 803 and 804 and an auxiliary windings 817 which are
electrically isolated from both energy windings 803 and 804 but may
be magnetically coupled to energy winding 804. The possible
generator 806 embodiments are explained in the descriptions of
FIGS. 3A-3L and 6A-6L. The induction generator 806 with the two
isolated energy windings 803 and 804 along with an energy storage
flywheel 814 allows multiple modes of operation which may be set by
user inputs 918 to master controller 893. The modes of operation
that are possible with system 800 are as follows:
[0158] a) AC power grid 807 may drive induction generator 806 as a
motor via energy windings 803 and conditioned power may be
delivered to energy windings 804 as an induction generator with
auxiliary windings 817, according to embodiments of the present
invention, providing control of the quality of the outputs 809 in
response to feedback signals load voltage 812 and load current 815
and generator controller 805. Generator controller 805 would switch
capacitors in auxiliary winding 817 in response to processing of
parameters of load voltage 812 and load current 815 by suppling
control signals (e.g., CN1 147, CN2 157 and CN3 167) to control
elements (e.g., 750, 760 and 770). In this mode, engine 818 would
be de-coupled (e.g., with a clutch) or free wheeling. Engine 818
may also be de-coupled by idling while remaining ready for
operation in another mode.
[0159] b) In another mode, engine 818 may be coupled to induction
generator 806, and by controlling the speed of engine 818,
induction generator 806 may supply power to both AC power grid 807
and load 810 through energy windings 803 and 804 respectively.
Induction generator 806, with auxiliary windings 817, provides
control of the quality of the outputs 809 in response to feedback
signals load voltage 812 and load current 815 and generator
controller 805. Generator controller 805 would switch capacitors in
auxiliary winding 817 in response to processing of parameters of
load voltage 812 and load current 815 by suppling control signals
(e.g., CN1 147, CN2 157 and CN3 167) to control elements (e.g.,
750, 760 and 770). c.) A third mode occurs if the AC power grid
fails (e.g., shorts) while running in mode "a" above. A failure may
be detected by monitoring lines 808 via controller 805. A signal
820 from controller 805 would disconnect the AC power grid 807 with
switch 821. Energy storage inertia 814 would maintain the
rotational speed of generator 806 and controller 805 would control
the capacitors in auxiliary windings 817 to optimize the generator
806 for a self-excited mode in response to parameters of load
voltage 812 and load current 815. Master controller 893 would
signal a set point speed for engine control 811 which would couple
and stabilize a idling engine 818 to the required speed. Because
the energy windings 803 and 804 are electrically isolated and
auxiliary windings 817 are isolated from energy windings 803, the
failure of AC power grid 807 does not adversely affect stored
energy in induction generator 806 before the switch 821 disconnects
the lines 808. If a "blinkless" (where the variable electrical load
810 (e.g., lighting system) does not experience any significant
variation of supplied outputs 809 due to the loss of AC power grid
807) system is desired in this mode, then engine 818 may be
maintained at a speed corresponding to a load condition so starting
delay and or delay in establishing a speed from an idle speed is
minimized.
[0160] c) Another mode similar to mode "c" occurs when induction
generator 806 is running in a line excited mode where energy from
engine 818 is supplying both the AC power grid 807 and load 810. A
failure in AC power grid 807 is detected and switch 821 is signaled
(via control signals 897) to disconnect the AC power grid 807. In
this mode, flywheel 814 maintains speed while engine control 811
receives and controls to a set point from master control 893 or
generator controller 805 in response to parameters of load voltage
812 and load current 815. Generator controller 805 determines and
switches in capacitance to auxiliary winding 817 to change
induction generator 806 from a line excited to a self excited mode
according to embodiments of the present invention.
[0161] d) An additional mode occurs when switch 821 disconnects
energy winding 803, switch 830 disconnects energy winding 804 and
switch 822 connects the power grid 807 directly to the load
838.
[0162] FIG. 9 is another induction system 900 employing an
induction generator 906 according to embodiments of the present
invention. AC power grid 907 has three phase lines 908 (either
inputs or outputs) coupled to energy windings 903 via switch 921.
Induction generator 906 is coupled to a variable electrical load
910 via load switch 930 with three phase energy windings 904 which
generate outputs 909. Induction generator 906 also has auxiliary
windings 917 configured according to embodiments of the present
invention and controlled by controller 905. Controller 905 receives
feedback signals load voltage 915 and load current 912 from
variable electrical load 910. An engine 913 is coupled to induction
generator 906 via a shaft 916 and is operable to supply rotational
mechanical energy. Engine 913 is controlled by engine controller
911 which is coupled to master controller 893 with signals 891.
Master controller 893 sends mode information and receives signals
from controller 905 via signals 892. Induction generator 906 also
may also optionally have an inertial energy storage element
(flywheel) 814. Engine controller 911 operates according to the
description of the engine controller in FIG. 11. Signal lines 797
allows generator controller 905 and engine controller 911 to
communicate directly.
[0163] The induction system 900 uses induction generator 906 which
has two electrically and magnetically isolated energy windings 903
and 904 and auxiliary windings 917 which are electrically isolated
from both energy windings but may be magnetically coupled to energy
winding 904. The possible generator 906 embodiments are explained
in the descriptions of FIGS. 3A-3L and 6A-6L. The induction
generator 906 with the two isolated energy windings 903 and 904
along with an energy backup inverter 914 powered by a battery
source 919 allows multiple modes of operation which may be set by
user inputs 918 to master controller 893. The modes of operation
that are possible with system 900 are as follows:
[0164] a) AC power grid 907 my drive induction generator 906 as a
motor via energy windings 903 and conditioned power may be
delivered to energy windings 904 as an induction generator with
auxiliary windings 917, according to embodiments of the present
invention, providing control of the quality of the outputs 909 in
response to feedback signals load voltage 915 and load current 912
and generator controller 905. Generator controller 905 would switch
capacitors in auxiliary winding 917 in response to processing of
parameters of load voltage 915 and load current 912 by suppling
control signals (e.g., CN1 147, CN2 157 and CN3 167) to control
elements (e.g., 750, 760 and 770). In this mode, engine 913 would
be de-coupled (e.g., with a clutch) or free wheeling. Engine 913
may also be de-coupled by idling and ready for operation in another
mode.
[0165] b) In another mode, engine 913 may be coupled to induction
generator 906 and by controlling the speed of engine 913, and
induction generator may supply power to both AC power grid 907 and
load 910 through energy windings 903 and 904 respectively.
Induction generator 906, with auxiliary windings 917 provides
control of the quality of the outputs 909 in response to feedback
signals load voltage 912 and load current 915 and generator
controller 905. Generator controller 905 would switch capacitors in
auxiliary windings 917 in response to processing of parameters of
load 5 voltage 915 and load current 912 by suppling control signals
(e.g., CN1 147, CN2 157 and CN3 167) to control elements (e.g.,
750, 760 and 770).
[0166] c) A third mode occurs if the AC power grid fails (e.g.,
shorts) while running in mode "a" above. A failure may be detected
by monitoring lines 908 via controller 906 monitoring. A signal 920
from controller 905 would disconnect the AC power grid 907 with
switch 921. Energy storage inverter 914 with battery source 919
would maintain the rotational speed of generator 906 and controller
905 would control the capacitors in auxiliary windings 917 to
optimize the generator 906 controlling the output quality of
outputs 909 in response to parameters of load voltage 915 and load
current 912. Because the energy windings 903 and 904 are
electrically isolated and auxiliary windings 917 are isolated from
energy windings 903, the failure of AC power grid 907 does not
adversely affect stored energy in induction generator 906 before
the switch 921 disconnects the lines 908. A "blinkless" (where the
variable electrical load 910 (e.g., lighting system) does not
experience any significant variation of supplied outputs 909 due to
the loss of AC power grid 907) system is possible in this mode.
[0167] d) Another mode similar to mode "c" occurs when induction
generator 906 is running in a line-excited mode where energy from
engine 913 is supplying both the AC power grid 907 and load 910. A
failure in AC power grid 907 is detected and switch 921 is signaled
to disconnect the AC power grid 907. In this mode, energy storage
inverter 914 with battery source 919 maintains speed of generator
906 (operating it as a motor) while engine control 911 receives and
controls engine 913 to a set point speed received from master
control 893 in response parameters of load voltage 915 and load
current 912. The system 900 may not have an engine 913 at all and
operate with energy storage inverter 914 with battery source 919 as
the only backup.
[0168] Because of the isolation of the energy windings 903 and 904
and the isolation of the auxiliary windings 917 from the energy
windings 903 connected to the AC power grid 907, a failure in the
AC power grid 907 (e.g., a short circuit) does not affect the
operation of induction generator 906 immediately allowing time for
the fault to be detected and for switch 921 to take the AC power
grid 907 off-line. Inverter 914 and battery source 919, along with
feedback control of auxiliary control windings 917 allows the
induction generator to be controlled and thus the voltage output to
the load remains stable. Inverter 914 may be maintained or engine
913 may be brought up to speed and coupled to induction generator
906 allowing inverter 914 to be removed. In either case the
feedback control of auxiliary windings 917 with controller 905
maintains a stable output for this "blinkless" system. The fast
response of controller 905 and auxiliary windings 917 according to
embodiments of the present invention, enables a system 900 to
operate "blinkless" where the variable electrical load 910 (e.g.,
lighting system) does not experience any significant variation of
supplied outputs 909 due to the loss of AC power grid 907.
Additional switch 922 allows switches 921 and 930 to disconnect the
induction generator 906 and power grid 907 to supply load 910
directly.
[0169] FIGS. 10A and 10B are circuit diagrams of analog and digital
circuits which may be used according to embodiments of the present
invention. FIG. 10A illustrates three phase energy winding 1007
which comprises branch energy windings 1009, 1008 and 1010. Loads
1004, 1005 and 1006 are coupled between terminals A11, B11 and C11
and node 1018 respectively. Three phase energy winding 1007 may be
any one of the three phase winding configurations explained in
embodiments of the present invention (e.g., FIGS. 1A-1L, 3A-3L and
6A-6L. Current transformer 1003 is an analog component that may be
used to sense the load current through load 1004. Other sense
elements may also be used (e.g., a series sense resistor or Hall
effect devices). The output of current transformer 1003 is coupled
to an isolation and conditioning amplifier 1020 which generates a
voltage VIL 1001 which is proportional to the load current in load
1004. Likewise, conditioning amplifier 1021 is used to sense the
load voltage across load 1004 and generate a voltage VVL 1002 which
is proportional to the load voltage across load 1004. Other
embodiments of the present invention may sense all three phase load
currents and voltages in the case the loads are unequal, in which
case further processing of all three signals may be done to
determine an appropriate feedback response.
[0170] FIG. 10B is a circuit diagram illustrating further
processing of the signals VIL 1001 and VVL 1002. Signals VIL 1001
and VVL 1002 are coupled to an exemplary analog to digital (A-D)
converter 1013 which produces digital outputs 1022. A-D converter
1013 may digitize more than one parameter of signals VIL 1001 and
VVL 1002, for example amplitude, frequency, and phase angle.
Micro-controller 1014 may be any of a variety of commercially
available micro-controllers which are operable to perform the
function in FIG. 10B (e.g., Intel 8051). Alternately, a
micro-controller may have the A-D function built into the unit
along with other programmable functions. Micro-controller 1014
generates outputs 1016 for control elements (e.g., control elements
750, 760 and 770 for the auxiliary control winding 126 in FIG. 1H)
of auxiliary windings 1017 in induction generator 1015. Outputs
1016 may comprise signals for a auxiliary windings like auxiliary
windings 140 in the embodiment of FIGS. 1K and 1L. Micro-controller
1014 would also generate outputs and receive inputs 892 which are
coupled to master controller 893. The controller 1011 may be used
for the implementation of any of controllers 784, 793, 855, 805,
and 905. Micro-controller 1014 also receives and sends control
signals 797 to an engine controller (e.g., 911, 811, and 783) as
described in embodiments of the present invention.
[0171] FIG. 11 is a block diagram of an engine controller 1101.
Engine controller 1101 may be used in any of the systems 780, 800,
and 900 for engine controllers 783, 811, 861 and 911 respectively.
Signals VIL 1001 and VVL 1002 are derived load parameter signals
from FIG. 10A. A-D converter 1103 generates digital signals 1112
which are coupled to micro-controller 1014. In one embodiment of
the present invention, only one micro-controller 1014 may used in
both the engine controller and the auxiliary winding controller.
Modem low cost micro-controllers are fast enough to provide both
control functions. Micro-controller 1014 generates output signals
1109 which are coupled to an electromechanical driver circuit 1105.
Drive circuit 1105 has an output 1113 and may be a solenoid, linear
motor or stepping motor driver. Signals 1107 may control other
electromechanical or electronic devices (not shown) on engine 1010
(e.g., ignition circuits). Electro-mechanical device 1102 is
coupled to throttle device 1108 through a coupling rod 1106, which
moves in both directions to speed up and slow down engine 1010 by
controlling a fuel valve (not shown). Electro-mechanical device
1102 may be a linear stepping motor, a rotary stepping motor with
an actuating screw or an indexing solenoid device. A particular
electromechanical device 1102 may have its drive circuitry
contained within and receive only control signals from
micro-controller 1014. Even though micro-controller 1014 may be
used for both the engine and auxiliary winding controllers, their
control algorithms would be different and would be incorporated in
control code within micro-controller 1014. The control code in
micro-controller 1014 may be modified depending on a particular
engine 1010 and the particular generator embodiment it is
controlling.
[0172] Engine controller 1101 may not use the load signals 1001 and
1002 but rather receive set point data on signals 891 from a master
controller or a generator controller. In this embodiment,
micro-controller 1014 would receive an engine speed signal 1107 and
use control algorithms to send signals to throttle 1102 to bring
engine 1010 into speed control. The algorithms and the
micro-controller 1014 operate with high speed electromechanical
actuators and electronic ignition devices on engine 1010 to produce
an engine speed control system that is fast and with a controlled
and near critically damped response when changing between a present
speed and a new set point speed.
[0173] Referring to FIG. 12, throughout the description of the
various embodiments of the present invention, reference is made to
an engine control, or controller, primarily for controlling
operation of the prime mover engine, and a controller for auxiliary
(aux.) control windings, or generator control, or controller,
primarily for controlling the operation of the generator. More
specifically, the generator control operates to control the
switching in or switching out of capacitors in the auxiliary
windings of the various embodiments. A master control or controller
1201 operates to provide master control over the engine control
1202 and the generator control 1203. Furthermore, in some of the
embodiments of the present invention, the master control 1201 will
receive inputs from sensors and/or operate switches 1204, such as
to switch in or out the load or to switch in or out the power
grid.
[0174] As will be further described with respect to FIGS. 14 and
15, the engine control 1202 also includes a firing circuit 1205 and
a throttle control, or controller 1206.
[0175] Referring to FIG. 13, there is illustrated a flow diagram
for a process implemented within the master control 1201, as
illustrated in FIG. 12. In step 1301 a start initializes the
generator and may involve applying a direct current (DC) to one of
the windings to establish a residual magnetic field in the
induction generator. In step 1302, the master control 1201 operates
to receive user inputs 1207 as to a particular mode in which the
system is to operate. Such modes, as described previously, include
a backup mode, a stand-alone mode, a full generator output parallel
mode, a balanced load parallel mode, a line conditioning mode, and
all other modes described herein. Once the master control 1201 has
received inputs informing it of its particular mode of operation,
the master control 1201 will then determine the states of the
engine and generator in step 1303. Such states of the engine and
generator may include whether the engine is running, in a startup
phase, in a standby state, or engaged with a load. Master control
1201 may also determine whether the generator is energized, and may
also determine whether a power grid is coupled to the system. More
particularly, the voltage and current magnitudes of the load,
generator outputs, and/or grid inputs may also be sensed. Step 1302
may be performed in a manual fashion with a user inputting these
various parameters, or may be performed automatically using various
sensors coupled to the engine, generator, load, and power grid.
[0176] Next, in step 1303, if the mode of operation includes the
implementation of a prime mover engine driving the generator, then
the master control 1201 will determine what state the engine is in.
For example, if the engine is idle, the master control 1201 will
send a signal to the engine control 1202 to initiate the engine
startup sequence, which is described more particularly with respect
to FIG. 14. In step 1304, the master control 1201 will determine if
the generator is energized (the energy windings energized). If the
generator is not energized, then the master control 1201 will send
a signal, or message, to the generator control 1203 to energize its
energy windings, which is described in more detail with respect to
FIG. 16.
[0177] In step 1305, the master control 1201 will also send a
message to the generator control 1203 and, if applicable, the
engine control 1202 as to what mode of operation is being
implemented and the initial RPM (revolutions per minute) set points
which the engine is to operate. If the Engine is OFF, a message is
sent to the engine control to initiate an Engine start up sequence.
Thereafter, in step 1306, if a software switch is implemented in
the system to switch in or out the load from the generator, then an
optional step can be performed whereby the master control 1201
signals the switch to connect the load to the generator. Note, as
an option to such a software switch, an electromagnetic switch,
such as a solenoid switch, could be utilized to switch in and out
the load from the generator. Such an electromagnetic switch would
operate automatically without any control inputs to switch in the
load if sufficient voltage and current is present on the output of
the generator to the load, and switch out the load if such
sufficient voltage and current are not present.
[0178] Referring to FIG. 14, there is illustrated the startup
sequence for the prime mover engine. The process might begin in
step 1401, such as in response to the message received from the
master control 1201 in step 1303 described with respect to FIG. 13.
Thereafter, the startup sequence proceeds to step 1402 to monitor
for the presence of a fuel for the engine. Such a monitor may be
sensing the presence of a fuel pressure. Thereafter, in step 1403,
the engine throttle is opened for startup. Next, in step 1404, a
time delay is allowed for the fuel to pass to the carburetor. In
step 1405, the firing circuit 1205 is energized, and the starter is
engaged in step 1406. The starter will remain engaged until a
threshold oil pressure is measured putting the engine in a standby
state 1407. Such a standby state may be a predetermined RPM
monitored by a sensor on the flywheel of the engine.
[0179] Referring to FIG. 15, there is illustrated a flow diagram
implemented within the engine control of the various embodiments
when an engine is applicable to the mode of operation of the
system. As noted in the description of the engine startup sequence
of FIG. 14, the engine will be placed in a standby state 1407.
Next, in step 1501, the engine control will have received the
specified operating mode and initial load frequency set points from
the master control 1201, as described with respect to step 1305 in
FIG. 13. Monitoring and controlling to engine RPMS would be an
indirect and possibly a less accurate method of control.
Preferably, the frequency of the load voltage is used to control
the engine speed. Only in those cases where the engine is not yet
driving the induction generator would it be preferable to use RPMS
as a control parameter. In step 1502, a determination will be made
whether the frequency set points have been updated. This
determination may be made by monitoring whether the values within a
specified set of registers have been updated. The updating of these
frequency set point registers is further described with respect to
steps 1608 and 1610 in FIG. 16. If the frequency set points have
been updated, then the process will use these updated frequency set
points in step 1504. However, if the frequency set points have not
been updated, then the initial set points sent from the master
control 1201 will be utilized in step 1503.
[0180] Thereafter, in step 1505, the frequency of the load voltage
and any change in the frequency from a previous frequency setting
will be monitored. In step 1506, if the monitored frequency is at
the designated set points of either of steps 1503 or 1504, then the
process will merely return to step 1502. If the frequency monitored
in step 1505 is not at the designated set points, the process will
proceed to step 1507 to determine if the frequency of the load
voltage is now greater than the designated set points. If the
frequency of the load voltage is greater than the designated set
points, then the process will proceed to step 1509 to reduce the
throttle settings on the engine according to a pre-selected
algorithm implemented within engine control 1202. If the frequency
of the load voltage is less than the designated set points, then
the process will proceed to step 1508 to increase the throttle
settings according to the selected algorithm. In steps 1508 and
1509 the process returns to step 1502.
[0181] Embodiments of the present invention utilize a throttle
control algorithm that is faster than typical engine throttle
control systems, by implementing a fast near critically damped
response to the frequencies of the load voltage, which is
sufficient to respond to the dynamic conditions of the system with
an engine overshoot that is within an acceptable threshold.
[0182] FIG. 16 illustrates a flow diagram implemented within the
generator control 1203. In step 1601, a determination is made as to
whether the load is connected. If the load is not connected, then a
wait is initiated until load connection. As described with respect
to FIG. 13, the master control 1201 may have already switched in
the load to the energy windings of the generator. Or, an
electromagnetic switch may have automatically switched in the load
to the energy windings of the generator.
[0183] When the load is connected, then in step 1602 load
parameters measured from the load are sensed. Such parameters may
include the voltage and current levels, the instantaneous change in
voltage, the instantaneous change in current, the phase angle, etc.
As a result of this measurement of the load parameters, the
generator can be in a balanced state, an overload state, or an
under-load state. This is determined in steps 1603 and 1605. In
step 1603, a determination is made whether the load is balanced. If
the load is balanced, then the process returns to step 1602. If the
load is not balanced, then a determination is made whether an
overload condition is occurring where the load is greater than the
generator output (L>G). This can be determined by determining
whether the voltage is sagging and the current is increasing. Note,
in one embodiment of the present invention, the voltage sag is
checked first by the process.
[0184] If the load is greater than the generator output, then the
process proceeds to step 1607 to switch in more capacitance into
the auxiliary windings in accordance with a predetermined
algorithm. This will increase the excitation field strength within
the generator. In step 1608, the throttle is adjusted as a function
of the frequency of the load voltage. The process then returns to
step 1604.
[0185] If in step 1605, it is determined that the load is less than
the generator output, in other words, the voltage is increasing and
the current is sagging, then the process will proceed to step 1606
to switch out capacitance within the auxiliary windings of the
generator according to a pre-selected algorithm. In step 1610, the
throttle is again adjusted as a function of the output frequency.
The process returns to step 1604.
[0186] The algorithms utilized by steps 1607 and 1606 may be
implemented in one of various manners. In one embodiment, the
switching capacitors described previously can be switched in
monotonically, one value increment at a time. Alternatively,
capacitors can be switched in as a function of the magnitude of the
voltage and/or current increase or decrease sensed in steps 1604.
Other algorithms for switching in the switched capacitors may be
utilized, and the present invention should not be limited to any
one particular algorithm.
[0187] FIG. 17 is a flow diagram of method steps according to
embodiments of the present invention for controlling an induction
generator. In step 1701, an induction machine (generator/motor) is
would with auxiliary windings that are electrically and
magnetically isolated from its energy windings. In step 1702,
capacitors of different weighted values are coupled via
electrically controllable alternating current switches (e.g., a
Triac) across a portion of each auxiliary winding. In step 1703,
the induction machine is rotated either by a mechanically coupled
engine or by a power line excitation of the energy windings. In
step 1704, voltage and current parameters of the of the energy
windings are measured. These may include magnitude of the voltage
and current, frequency of the voltage, as well as phase between
voltage and current. In step 1705, selected capacitors are switched
into or out of the auxiliary windings according to selected
algorithms to maintain the amplitude and power factor of energy
delivered to a load. In the method of FIG. 17, the same magnitude
capacitors are not required to be switched into or out of each
winding, rather the windings may have different values of
capacitors. In step 1706, selected parameters of a prime mover
engine mechanically coupled to and rotating the induction machine
are controlled in response to the measured parameters of the energy
winding, the selected capacitor values, and user inputs setting
desired set parameters for the energy delivered to the variable
load
[0188] Although the present invention and its advantages have been
described in detail, it should be understood that various changes,
substitutions and alterations can be made herein without departing
from the spirit and scope of the invention as defined by the
appended claims.
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