U.S. patent application number 10/773265 was filed with the patent office on 2004-08-12 for permanent magnet alternator and voltage regulator for regulating the output voltage of a permanent magnet alternator.
Invention is credited to Edmundson, William C., Murray, Ronald E., Stevens, Julius J., Young, Craig G..
Application Number | 20040155546 10/773265 |
Document ID | / |
Family ID | 28453150 |
Filed Date | 2004-08-12 |
United States Patent
Application |
20040155546 |
Kind Code |
A1 |
Stevens, Julius J. ; et
al. |
August 12, 2004 |
Permanent magnet alternator and voltage regulator for regulating
the output voltage of a permanent magnet alternator
Abstract
A permanent magnet alternator including a stationary stator
including a plurality of spaced stator poles projecting inwardly
from the stator, a winding circuit wound through the spaces between
the stator poles, a rotor assembly mounted for rotation within the
stator, including a plurality of permanent magnets fixedly mounted
on an outer circumferential surface of the rotor in alternating
polarity, and a retaining shield for reducing the effects of
centrifugal motion of the rotor during operation of the alternator.
A voltage regulator circuit is also provided for applying the
output of the permanent magnet alternator having at least one
stator mounted coil to a load, and includes a rectifier circuit
having an output and an input adapted to be connected to a stator
mounted coil for converting alternating potential to a time varying
single potential on the output, a current control circuit connected
between the output of the rectifier circuit and the load, an
instantaneous voltage sensing circuit connected with the output of
the rectifier circuit and the current control circuit for measuring
the instantaneous voltage appearing on the output and for causing
the current control circuit to assume its conductive state when the
instantaneous voltage is above a predetermined amount, and a
regulator control circuit for sensing the voltage applied to the
load by the current control circuit and for causing the current
control circuit to assume its non conductive state when the voltage
applied to the load is above a desired level and for shortening the
time during which the current control circuit is in its conductive
state as the voltage applied to the load approaches the
predetermined level.
Inventors: |
Stevens, Julius J.; (Fort
Deposit, AL) ; Edmundson, William C.; (Winona Lake,
IN) ; Murray, Ronald E.; (Prattville, AL) ;
Young, Craig G.; (Prattville, AL) |
Correspondence
Address: |
NIXON PEABODY, LLP
401 9TH STREET, NW
SUITE 900
WASINGTON
DC
20004-2128
US
|
Family ID: |
28453150 |
Appl. No.: |
10/773265 |
Filed: |
February 9, 2004 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10773265 |
Feb 9, 2004 |
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10109667 |
Apr 1, 2002 |
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6690145 |
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60280153 |
Apr 2, 2001 |
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Current U.S.
Class: |
310/156.01 |
Current CPC
Class: |
H02P 2101/30 20150115;
H02K 1/278 20130101; H02K 9/06 20130101; H02P 2101/45 20150115;
H02K 11/046 20130101; H02P 9/48 20130101; H02K 1/30 20130101; H02K
1/2793 20130101 |
Class at
Publication: |
310/156.01 |
International
Class: |
H02K 021/12 |
Claims
What is claimed is:
1. A permanent magnet alternator comprising: a stator including a
stator body and a plurality of spaced stator poles projecting
inwardly from said stator body; a winding circuit wound through the
spaces between said plurality of stator poles, a rotor assembly
mounted for rotation within said stator body, said rotor assembly
including a rotor body; a plurality of permanent magnets fixedly
mounted on an outer circumferential surface of said rotor body in
alternating polarity; and retaining means for reducing the effects
of centrifugal motion of said rotor body during operation of said
alternator, said retaining means being positioned between said
plurality of permanent magnets and said stator poles.
2. The permanent magnet alternator as defined by claim 1, wherein
said retaining means comprises a cylindrical sleeve.
3. The permanent magnet alternator as defined by claim 2, wherein
said cylindrical sleeve comprises a non-ferromagnetic material.
4. The permanent magnet alternator as defined by claim 3, wherein
said non-ferromagnetic material is stainless steel.
5. The permanent magnet alternator as defined by claim 1, wherein
said rotor body comprises a non-ferromagnetic material and said
outer circumferential surface of said rotor body comprises a
ferromagnetic material.
6. The permanent magnet alternator as defined by claim 5, wherein
said non-ferromagnetic material is aluminum and said ferromagnetic
material is steel.
7. The permanent magnet alternator as defined by claim 1, wherein
said winding circuit is a multiphase winding circuit.
8. The permanent magnet alternator as defined by claim 7, wherein
said multiphase winding circuit is a three phase winding
circuit.
9. The permanent magnet alternator as defined by claim 1, wherein
said rotor assembly includes a first rotor body and a second rotor
body.
10. A permanent magnet alternator comprising: a stator assembly
including a stator body and a plurality of spaced stator poles
projecting inwardly from said stator body; a winding circuit wound
through the spaces between said plurality of stator poles; a rotor
assembly mounted for rotation within said stator body, said rotor
assembly including a rotor body and a plurality of fan-like
projections spaced equidistant along said rotor body; a plurality
of permanent magnets fixedly mounted on an outer circumferential
surface of said rotor body in alternating polarity; and retaining
means for reducing the effects of centrifugal motion of the rotor
body during operation of said alternator, said retaining means
being positioned between said plurality of permanent magnets and
said stator poles, wherein each of said fan-like projections
project outwardly from said rotor body along a plane lying
substantially parallel relative to an outer surface of said rotor
body so as to reduce the ambient temperature within said alternator
during rotation of said rotor body.
11. A permanent magnet alternator comprising: a stator including a
stator body and a plurality of spaced stator poles fixedly mounted
on said stator body, each of said plurality of stator poles
projecting outwardly along a plane lying substantially parallel
relative to an outer circumferential surface of said stator body; a
winding circuit wound through the spaces of said plurality of
stator poles; a rotor including a rotor body mounted in opposition
to said stator body; and a plurality of permanent magnets fixedly
mounted on said rotor body in alternating polarity, each of said
plurality of permanent magnets projecting outwardly along a plane
lying substantially parallel relative to an outer circumferential
surface of said rotor body, wherein said rotor body is operatively
positioned relative to said stator body such that said plurality of
permanent magnets are rotateably aligned with said plurality of
stator poles so as to generate a continuous alternating flux
density magnetic field along a primary flux path.
12. A regulator for applying the output of a permanent magnet
alternator having at least one stator mounted coil to a load, said
regulator comprising: a rectifier circuit having an output and an
input adapted to be connected to a stator mounted coil for
converting alternating potential into a time varying potential on
said output; a current control circuit connected between said
output of said rectifier circuit and the load and for cycling
between (1) a conductive state to conductively connect said
rectifier circuit with the load and (2) a non-conductive state to
isolate said rectifier circuit from the load; an instantaneous
voltage sensing circuit connected with said output of said
rectifier circuit and said current control circuit for measuring
the instantaneous voltage appearing on said output and for causing
said current control circuit to assume its conductive state when
said instantaneous voltage is above a predetermined amount; and a
regulator control circuit for (1) sensing the voltage applied to
the load by said current control circuit and for causing said
current control circuit to assume its non conductive state when the
voltage applied to the load is above a desired level and (2) for
shortening the time during which said current control circuit is in
its conductive state as the voltage applied to said load approaches
the predetermined level.
13. A regulator as defined in claim 12, wherein said regulator
control circuit includes a sensing circuit for determining if a
short circuit exists by measuring the period of time said current
control circuit is in a conductive state.
14. A regulator as defined in claim 12, wherein said regulator
control circuit includes an input connected with an RC circuit for
adjusting the operating voltage of said regulator circuit in
response to changes in the duty cycle of said current control
circuit.
15. A regulator as defined in claim 12, further including an
alternator failure indicator responsive to an over voltage or under
voltage condition to produce an alternator failure condition.
16. A regulator as defined in claim 12, further including a load
dump circuit selectively connectable in parallel with said load,
said load dump circuit being connected in parallel when the voltage
applied to the load continues to increase for more than a
predetermined period.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention is directed generally to a light
weight alternator, and in particular, a permanent magnet-type
alternator including a voltage regulator for regulating the voltage
output of the permanent magnet-type alternator.
[0003] 2. Field of the Related Art
[0004] Various alternators use wound stator and rotor assemblies in
which an electromagnetic force is produced in and around the rotor
windings by admitting current through the rotor windings. In such
designs, as the magnetic field produced in the spinning rotor
couples with the windings at the stator, current is induced in the
stator windings. These alternators, however, require brushes or
slip rings to maintain a closed circuit for admitting the current
necessary in the rotor during rotation. Because the brushes or slip
rings are mechanical connections, they are susceptible to wear and
corrosion.
[0005] The use of permanent magnet alternators have been found to
be advantageous since they do not require that current be supplied
to the rotor. In other words, the field inherent to and produced by
the magnetic material of the permanent magnet alternators induces
current in the stator as the magnet poles move in respect to the
stator windings. Because it is not required to supply current to
the rotor, slip rings and brushes are not required.
[0006] While the use of permanent magnet alternators have proven
successful for various applications, the prior art systems have
several shortcomings. Generally, because the alternator generates
excessive heat, internal fans are provided on the drive end to cool
the windings and the rotor. This increases the weight of the
alternator, and thus, makes it undesirable for use in an automotive
or aerospace capacity where fuel efficiency is needed. Moreover,
many systems require the attachment of individual magnets to the
outer circumferential surface of the rotor, which may result in the
failure of the alternator if by chance one or more magnets becomes
detached from the rotor due to the high centrifugal forces that
result from the rotation of the rotor at high rpm or faulty
adhesion between the magnet and surface. Yet another problem
associated with permanent magnet alternators is the difficulty
associated with controlling the output voltage generated in the
stator windings as will otherwise inherently occur when the
alternator is driven at variable rotational velocities. These
drawbacks of the prior art are especially problematic in the
vehicular environment where low cost, high reliability and light
weight are all important to achieving a commercially acceptable
design.
SUMMARY OF THE INVENTION
[0007] In view of the foregoing, it is an object of the present
invention to overcome the disadvantages in the related art by
providing a permanent magnet alternator for use in an automotive or
aerospace capacity that is of a size that allows it to be placed in
small areas of an automobile or aircraft engine compartment.
[0008] It is another object of the present invention to provide a
permanent magnet alternator that is light-weight and highly
efficient.
[0009] It is a yet another object of the present invention to
provide a permanent magnet alternator that has a high cooling
capacity.
[0010] It is still another object of the invention to provide a
permanent magnet alternator that allows the rotation of the rotor
at high rpm without resulting in the detachment of magnets from the
rotor.
[0011] It is yet a further object of the invention to provide a
permanent magnet alternator with a voltage regulator that
independently regulates and controls the charging current produced
by the alternator.
[0012] These as well as other objects are achieved in accordance
with the invention including a permanent magnet alternator assembly
provided with a stationary stator, a rotor mounted for rotation
within the stator, a winding circuit for generating a magnetic
flux, a plurality of permanent magnets for attachment to the rotor,
and a retaining shield positioned between the rotor and stator for
reducing the effects of centrifugal motion of the rotor during
operation of the alternator.
[0013] The stator includes a substantially cylindrical core or body
in which a plurality of stator poles project radially inward from
the stator body. Each stator pole is composed of a longitudinal
shank portion including a base end which is attached to the stator
body and a distal end which is flared to facilitate ease during
assembly of the winding circuit.
[0014] The rotor has a substantially cylindrical body having a
laminated structure including a core section preferably comprising
a non-ferromagnetic material that is both light-weight and
non-corrosive such as aluminum, and an outer circumferential
surface preferably comprising a ferromagnetic material such as
steel or the like. The permanent magnets are fixedly mounted or
attached to the outer circumferential surface of the rotor body in
alternating polarity. In order to further reduce the overall weight
of the alternator, it is preferred that light-weight, yet high
field permanent magnets are used, such as those composed of
Neodymium-Iron-Boron (NdFeB).
[0015] The retaining shield is positioned between the stator poles
and the permanent magnets to reduce the effects of centrifugal
motion of the rotor body during operation of the alternator, and
the undesirable effects of vibration. The retaining shield is
preferably a cylindrical sleeve composed of a non-ferromagnetic
material such as stainless steel. The use of the retaining sleeve
is advantageous in that it reduces the centrifugal forces and
allows rotation of the rotor at high rpm without resulting in the
detachment of magnets from the rotor and the possible destruction
of the alternator.
[0016] In a second embodiment, the permanent magnet alternator
assembly includes a laminated, bifurcated rotor having a first
rotor section and a second rotor section, each rotor section having
a substantially cylindrical body composed of a light-weight,
non-ferromagnetic material such as aluminum, and an outer
circumferential surface composed of a ferromagnetic material such
as steel.
[0017] A plurality of fan-like projections are provided equidistant
on the peripheral surface of each rotor section. The placement of
the fans directly on the surface of each rotor section is
advantageous since it obviates the need for drive end fans for
cooling the rotors and windings, and thus, further reduces the
overall weight of the alternator. The fan-like projections project
outward from the side of each rotor section in order to provide the
efficient distribution of air inside the alternator housing. In
particular, the projections project along a plane that lies
substantially parallel relative to the outer circumferential
surface. In this way, high ambient temperatures produced inside the
alternator during rotation of the rotor are significantly
reduced.
[0018] A third embodiment of the invention includes a permanent
magnet alternator having a stator including a substantially
cylindrical body and a plurality of spaced stator poles that
project outward from a side surface of the stator body. In
particular, the stator poles project along a plane lying
substantially parallel relative to an outer circumferential surface
of said stator body.
[0019] A rotor is also provided including a substantially
cylindrical body mounted for rotation relative to the stator body
in a face-to-face spatial relationship, as opposed to the
conventional manner of rotating inside or outside of the stator.
Moreover, a plurality of permanent magnets are fixedly mounted
equidistant on the rotor body in alternating polarity and project
outward from a side surface of the rotor body. In particular, each
permanent magnet projects along a plane lying substantially
parallel relative to an outer circumferential surface of the rotor.
In this way, the rotor body may be operatively positioned relative
to the stator body such that the permanent magnets are rotatably
aligned in a face-to-face manner with the stator poles so as to
generate a continuous alternating flux density magnetic field along
a primary flux path.
[0020] The winding of the conductors or winding circuit on the
stator poles in accordance with this embodiment is advantageous
over conventional winding concepts in that the winding circuit does
not require being pulled around and over the outer circumferential
surface of the stator. This results in a less bulky design
radially, which is further advantageous in terms of weight.
[0021] Moreover, a voltage regulator circuit is also provided for
regulating the charging current produced by the permanent magnet
alternators described above. The regulator circuit is adapted to
receive the output of a 3-phase permanent magnet alternator,
however, other single phase or multi-phase permanent magnetic
alternators could be used to provide the input to the regulator
circuit.
[0022] The voltage regulator circuit in accordance with this
embodiment of the invention includes a rectifier circuit having an
output and an input adapted to be connected to a stator mounted
coil for converting alternating potential to a time varying single
potential on said output, a current control circuit connected
between the output of the rectifier circuit and the load and for
cycling between (1) a conductive state to conductively connect said
rectifier circuit with the load, and. (2) a non-conductive state to
isolate the rectifier circuit from the load. Also provided is an
instantaneous voltage sensing circuit connected with the output of
the rectifier circuit and the current control circuit for measuring
the instantaneous voltage appearing on the output and for causing
the current control circuit to assume its conductive state when the
instantaneous voltage is above a predetermined amount.
[0023] Last, a regulator control circuit is provided for (1)
sensing the voltage applied to the load by the current control
circuit and for causing the current control circuit to assume its
non conductive state when the voltage applied to the load is above
a desired level, and (2) for shortening the time during which the
current control circuit is in its conductive state as the voltage
applied to the load approaches the predetermined level. The
regulator control circuit may include a sensing circuit for
determining if a short circuit exists by measuring the period of
time the current control circuit is in a conductive state. The
regulator control circuit may further include an input connected
with an RC circuit for adjusting the operating voltage of the
regulator circuit in response to changes in the duty cycle of the
current control circuit.
[0024] The voltage regulator circuit may include an alternator
failure indicator responsive to an over voltage or under voltage
condition to produce an alternator failure indication. The voltage
regulator circuit may further include a load dump circuit
selectively connectable in parallel with the load, the load dump
circuit being connected in parallel when the voltage applied to the
load continues to increase for more than a predetermined
period.
BRIEF DESCRIPTION OF THE DRAWINGS
[0025] FIG. 1 illustrates a cross-sectional view of a permanent
magnet alternator assembly in accordance with a first embodiment of
the invention;
[0026] FIGS. 2(a) and 2(b) illustrate front and side views of
stator assembly in accordance with a first embodiment of the
invention;
[0027] FIGS. 3(a)-3(c) illustrate front, side and plane views of a
rotor assembly in accordance with the first embodiment of the
invention;
[0028] FIGS. 4(a) and 4(b) illustrate front and side views of a
retaining mechanism;
[0029] FIG. 5 illustrates a cross-sectional view of a permanent
magnet alternator assembly in accordance with a second embodiment
of the invention;
[0030] FIGS. 6(a) and 6(b) illustrate top and side views of the
rotor assembly and retaining shield in accordance with the second
embodiment of the invention;
[0031] FIG. 7 illustrates a plane view of a stator and rotor in
accordance with a third embodiment of the invention;
[0032] FIG. 8 illustrates a front view of a stator assembly in
accordance with a third embodiment of the invention; and
[0033] FIG. 9 illustrates a schematic diagram of a voltage
regulator for use in combination with the permanent magnet
alternator of the present invention.
DETAILED DESCRIPTION OF THE INVENTION
[0034] Referring now to FIGS. 1-4, which illustrate in a first
embodiment of the invention a permanent magnet alternator assembly
10 including a stationary stator 20, a rotor 30 mounted for
rotation within the stator, a winding circuit 40 for generating a
magnetic flux, a plurality of permanent magnets 50 for attachment
to the rotor 30, and a retaining shield 60 positioned between the
stator 20 and rotor 30 for reducing the effects of centrifugal
motion of the rotor 30 during operation of the assembly 10.
[0035] As shown in FIG. 1, to assembly the alternator 10, the
stator 20 is clamped between a two-piece housing 70. Preferably,
the housing 70 comprises a material that is non-ferromagnetic,
light-weight, non-corrosive and provides good heat dissipation. In
this regard, it is preferred that the material selected for the
housing 70 comprises aluminum. The housing 70 has first 71 and
second 72 housing sections that may be connected using any
conventional manner such as bolts, screws or the like. The rotor 30
is mounted for rotation on a rotor shaft 80 that extends from a
power source such as an engine (not shown) through the housing 70.
Bearings 90 are provided to support the rotor body 31 and are
mounted in the front and rear of the housing 70.
[0036] As illustrated in FIGS. 1, 2(a) and 2(b), the stator 20
comprises a substantially cylindrical core or body 21 in which a
plurality of stator poles 22 project radially inward from the
stator body 21. Each stator pole 22 comprises a longitudinal shank
including a base end 22a which is attached to the stator body 21
and a distal end 22b which is flared to facilitate ease during
assembly of the winding circuit 40. The stator body 21 and stator
poles 22 are preferably composed of a ferromagnetic metal such as
steel or the like.
[0037] As shown in FIGS. 3(a)-3(c), the rotor 30 comprises a
substantially cylindrical body 31 having a laminated structure. In
particular, the rotor body 31 includes a core section 32 preferably
comprising a non-ferromagnetic material that is both light-weight
and non-corrosive, and an outer circumferential surface 33
preferably comprising a ferromagnetic material. In this regard, it
is preferred that the non-ferromagnetic metallic material comprises
aluminum while the ferromagnetic material comprises steel.
[0038] The permanent magnets 50 are fixedly mounted or attached to
the outer circumferential surface 33 of the rotor body 31 in
alternating polarity. Preferably the permanent magnets 50 are
attached to the outer circumferential surface 33 using a suitable
adhesive that is not adversely effected by the high temperature and
stress environment of the alternator 10. In order to further reduce
the overall weight of the alternator 10, it is preferred that
light-weight, yet high field permanent magnets are used. In this
regard, the permanent magnets 50 may comprise high field
Neodymium-Iron-Boron (NdFeB).
[0039] As shown in FIGS. 1, 4(a) and 4 (b), the retaining shield 60
is positioned between the stator poles 22 and the permanent magnets
50 to reduce the effects of centrifugal motion of the rotor body 31
during operation of the alternator 10. Once the retaining shield 60
is installed, a radial air gap (not shown) is formed between the
retaining shield 60 and the stator 20 in order to prevent friction
during operation. The retaining shield 60 is a cylindrical sleeve
comprising a non-ferromagnetic material such as stainless steel.
However, the sleeve is not limited to stainless steel and may
comprise any material that exhibits high strength and high
corrosion properties during high temperature operation.
[0040] Referring now to FIG. 5, which shows a permanent magnet
alternator assembly 110 in a second embodiment of the invention,
including a stator 120, a rotor 130, a winding circuit 140, a
plurality of permanent magnets 150, and a retaining shield 160. The
stator 120, winding circuit 140, permanent magnets 150, and
retaining shield 160 each have the same structure as previously
described in the first embodiment.
[0041] As shown in FIGS. 5, 6(a) and 6(b), the rotor 130 is a
bifurcated-type comprising a first rotor section 130a and a second
rotor section 130b, each having a substantially cylindrical body
131a, 131b preferably comprising a non-ferromagnetic material such
as aluminum, an outer circumferential surface 132a, 132b preferably
comprising a ferromagnetic material such as steel.
[0042] A plurality of fan-like projections 133 are provided
equidistant on the peripheral surface of the rotor body 131a, 131b.
The placement of the fans directly on the surface of the rotor
sections 130a, 130b obviates the need for drive end fans for
cooling the rotors 130a, 130b and windings 140, and thus, further
reduces the overall weight of the alternator. The fan-like
projections 134a, 134b are triangular-shaped and project outwardly
from the side of the rotor body 131a, 131b in order to provide the
efficient distribution of air inside the housing 170. In
particular, the projections 133 project along a plane that lies
substantially parallel relative to the outer circumferential
surface 132a, 132b. In this way, high ambient temperatures produced
inside the alternator 110 during rotation of the rotor 130 are
significantly reduced. Although the projections 133 shown in FIGS.
5, 6(a) and 6(b) are triangular-shaped, they may take the form of
various different geometries in order to produce the desired
cooling effect.
[0043] During assembly of the alternator 110, each rotor section
130a, 130b is mounted for rotation on a rotor shaft 180 by press
fit. Bearings 180 are provided to support each rotor section 130a,
130b on the shaft 170. Like the first embodiment, the permanent
magnets 150 are fixedly mounted using a suitable adhesive to the
outer circumferential surface 133a, 133b of each rotor body 131a,
131b in alternating polarity.
[0044] As shown in FIG. 7, a third embodiment of the invention
includes a permanent magnet alternator 210 having a stator 220
including a substantially cylindrical body 221 and a plurality of
spaced stator poles 222 fixedly mounted on the stator body 221.
Each of the stator poles 222 project outwardly from a side surface
of the stator body 221. In particular, the stator poles 222 project
along a plane lying substantially parallel relative to an outer
circumferential surface of said stator body 221. Each stator pole
222 comprises a longitudinal shank including a base end 222a which
is attached to the stator body 221 and a distal end 222b which is
flared to facilitate ease during assembly of a winding circuit 240
through the spaces of the of stator poles 222. As in the
previously-described embodiments of the invention, the stator body
221 and stator poles 222 are preferably composed of a ferromagnetic
metal such as steel or the like.
[0045] A rotor 230 including a substantially cylindrical body 231
is mounted for rotation relative to the stator body 221 in a
face-to-face spatial relationship. A plurality of permanent magnets
250 are fixedly mounted equidistant on the rotor body 231 in
alternating polarity. In accordance with this embodiment, each of
the permanent magnets 250 project outward from a side surface of
the rotor body 231. In particular, each permanent magnet 250
projects along a plane lying substantially parallel relative to an
outer circumferential surface of the rotor body. Moreover, the
rotor body is operatively positioned relative to the stator body
such that the permanent magnets 250 are rotateably aligned in a
face-to-face manner with the stator poles 222 so as to generate a
continuous alternating flux density magnetic field along a primary
flux path.
[0046] FIG. 8 shows the construction of the winding circuit 250 on
the stator poles 222 in accordance with the third embodiment. The
winding circuit 240 is composed of a first winding portion 240a, a
second winding portion 240b, and a third winding portion 240c,
whereby each portion 240a, 240b, 240c is individually wound so as
to alternatively occupy every third space between the extending
stator poles 222. This design is also advantageous over
conventional wiring concepts in that the winding circuit 240 does
not require being pulled around and over the outer circumferential
surface of the stator 220.
[0047] To implement the subject invention, it is desirable to
provide a mechanism for regulating the charging current produced by
the permanent magnet alternators described above. For example,
reference is made to FIG. 9, wherein a suitable regulator circuit
300 is illustrated. This circuit 300 is specifically adapted to
receive the output of a 3-phase permanent magnet alternator, but
other single phase or multi-phase permanent magnetic alternators
could be used to provide the input to the regulator circuit
300.
[0048] Each phase of the alternator is formed by one or more stator
mounted coil(s) that are subjected to a time varying magnetic field
produced by rotation of the alternator rotor. Thus, each phase is
connected with a corresponding input 304a, 304b and 304c. As the
rotor rotates, a potential is developed in the corresponding
coil(s) that is applied to the full wave rectifier 306 formed by
diodes D4 through D9. Output from the full wave rectifier 306 takes
the form of a full wave rectified direct current voltage at point
A. The magnitude of this time varying voltage will depend on a
number of factors including the strength of each permanent magnet,
the speed of rotation of the rotor, the number of turns in each
alternator coil, the size of the load circuit, resistance
(including reactive) of each coil, and environmental factors such
as temperature. Unless otherwise noted, all voltage potentials of
the voltage regulator circuit 300 will be referenced to point B,
which is at ground potential.
[0049] The regulator circuit 300 of FIG. 9 includes a pre-regulator
circuit 308 for sensing the instantaneous voltage produced by full
wave rectifier 306 and for producing a control signal when the
instantaneous voltage exceeds a predetermined value. Regulator
circuit 300 further includes a current control circuit 310 for
alternating between a conductive state in which current is allowed
to flow into the load (for example, a battery 311) and a
non-conductive state in which current is prevented from flowing to
the load. FIG. 9 also illustrates the use of a comparison circuit
312 for responding to the voltage at point C in a manner to prevent
the voltage applied to the load from reaching an excessively high
level. An annunciator circuit 314 is provided to sense certain
potentially undesirable operating conditions.
[0050] A regulator control circuit 316, connected to input 304c,
current control circuit 310, comparison circuit 312 and annunciator
circuit 314, is illustrated in FIG. 9. As will be discussed more
fully below, regulator circuit 316 responds to sensed conditions to
produce appropriate control signals to implement desired operation
of the regulator circuit.
[0051] To understand the operation of the regulator circuit 300,
reference is again made to FIG. 9. In particular, pre-regulator
circuit 308 includes a series connection of zener diode D3 and
resistor RIO extending between point A and ground B. When D3
reaches its rated voltage, it breaks down causing a constant
voltage at the base of transistor Q5, a pnp-type transistor, which
becomes forward biased due to the voltage potential between its
base and emitter junctions. Current flows through the emitter to
collector junction of Q5 and applies a startup voltage to current
control circuit 310.
[0052] Referring now to current control circuit 310, there is
provided an npn transistor Q4 whose collector-emitter circuit is
connected between points A and C of the regulator circuit 300. Q4
toggles between a conductive state in which current is allowed to
flow from the full-wave rectifier to the load (i.e., battery 311)
and a non-conductive state in which current flow is effectively cut
off. The duty cycle of transistor Q4 controls the effective flow of
charging current to battery 311. The base of transistor Q4 is
connected with the emitter of npn transistor Q3. The collector of
Q3 is connected with the collector of Q4 such that upon Q5 becoming
forward biased, current is caused to flow through the emitter to
collector junction of Q5 to apply a startup voltage to the
transistor Q3.
[0053] Voltage applied to the base of Q3 from Q5 of the
pre-regulator circuit 308 causes the base to emitter junction of Q3
to become forward biased, which causes current to flow through Q3.
This situation causes a voltage potential to be applied to the base
of transistor Q4, an npn-type transistor, which becomes forward
biased because of the voltage potential difference between its base
and collector junctions. Thus, Q4 turns on and allows current to
flow through its collector to emitter junctions. This current will
flow into and charge the battery until the control signal from the
comparison circuit 312 is reduced to a point that Q3 of the control
element is turned off, which stops the current flow through Q4.
[0054] The voltage potential at point C is applied to the voltage
divider of R1 and R2. The sample point between R1 and R2 is applied
to pin 11 of regulator control circuit 316 which will be discussed
in more detail below. The desired voltage at C may be set by
adjustment of a variable resistor R2 which thus forms a
potentiometer.
[0055] Regulator control circuit 316 may take the form of an
integrated chip suitable for the application in which it is
required. One example of a suitable integrated circuit chip to form
circuit 316 would be a Motorola CS3351. The operating frequency of
circuit 316 may be set by selection of the value of C4 connected
between pin 4 and ground. A representative value of capacitor C4
would be 0.022 .mu.F, although this value could range between 0.010
.mu.F and 0.047 .mu.F. The operating voltage for regulator control
circuit 316 is established by an R-C circuit formed of resistor R3
and capacitors C1 and C2. The ground potential is applied to pin
2.
[0056] In operation, the alternator voltage is sensed at pin 10 of
regulator control circuit 316. If the voltage potential at point C
is below the pre-determined voltage potential set by adjustment of
R2, regulator control circuit 316 will provide an output voltage
potential at pin 1 sufficient in amplitude to forward bias the base
emitter junction of transistor Q1. This output voltage may be
termed a "drive voltage." This condition causes the collector to
emitter junction of Q1 to conduct. The voltage at the collector of
Q1 is 180 degrees out of phase with the voltage at the base of
transistor Q1 and is applied to the base of transistor Q2. Thus
transistor Q2 will operate in a complementary manner to transistor
Q1 to provide a voltage at the collector of Q2 that is in phase
with the output at pin 1 of regulator control circuit 316 and at a
sufficient voltage potential to forward bias the base emitter
junction of Q3 in the control circuit 310. Thus, the duty cycle of
current control circuit 310 is responsive to the output of
regulator control circuit 316.
[0057] Regulator control circuit 316 also operates to perform a
number of important safety control functions. For example, pin 14
operates to perform a short circuit monitor. In particular, if pin
1 and pin 14 are simultaneously high for a predetermined time
period, a short circuit is assumed and pin 1 is turned off removing
the drive voltage. When this voltage is removed, voltage potential
is removed from the base of Q2, Q3, and Q4 to thereby render the
current control circuit 310 non-conductive and thereby shut off
charging current to the battery. This causes the voltage potential
at point C to be reduced. As the voltage potential sensed at pin 11
begins to approach the desired cutoff potential, pin 1 begins to
change from a constant voltage potential to a square wave with the
on duty cycle becoming shorter the closer point C approaches the
desired predetermined voltage potential. In this way, voltage
regulation of the rectified permanent magnet alternator is
achieved.
[0058] The annunciator circuit 314 in association with the
regulator control circuit 316 is also provided to provide visual
warning of alternator failure and to operate a load dump circuit.
In particular, as illustrated in FIG. 9, a transistor Q6 is
provided with its emitter connected to ground and its base
connected to pin 5 of the regulator control circuit 316. The
collector is connected to the load through a switch Sw1, LED D2 and
resistor 7. Biasing resistors 6 and 9 are connected to pin 8 of the
regulator control circuit 316. If the alternator does not apply a
voltage to pin 10 of the regulator control circuit 316 or if the
voltage sensed at pin 11 indicates an over voltage condition, pin 5
outputs a voltage to the base of transistor Q6 which forward biases
the base to emitter junction of Q6. This current flows through R7
and forward biases LED D2 causing it to indicate an alternator
failure. If the regulator control circuit 316 is in an over voltage
condition, and the voltage potential continues to rise, the over
voltage indicating LED D2 will extinguish and the regulator control
circuit 316 will enter a load dump condition by causing transistor
Q6 to become conductive.
[0059] By way of example, the following commercially available
circuit elements may be used to form the regulator circuit
embodiment illustrated in FIG. 9.
[0060] R1 50 k ohm
[0061] R2 50 k ohm variable
[0062] R3 270 ohm
[0063] R4 22 k ohm
[0064] R5 10 k ohm
[0065] R6 22 k ohm
[0066] R7 1 k ohm
[0067] R8 10 k ohm
[0068] R9 2.2 k ohm
[0069] R10 100 ohm
[0070] R11 4.7 k ohm
[0071] C1 0.1 .mu.F
[0072] C2 10 .mu.F
[0073] C3 0.047 .mu.F
[0074] C4 0.022 .mu.F
[0075] Q1 ZTX 853
[0076] Q2 ZTX 853
[0077] Q3 NTE 54
[0078] Q4 MJ14002
[0079] Q5 ZTX 757
[0080] Q6 ZTX 853
[0081] D1 IN4004
[0082] D2 12V LED
[0083] D3 1N746A
[0084] D4 7771
[0085] D5 7771
[0086] D6 7771
[0087] D7 7771
[0088] D8 7771
[0089] D9 7771
[0090] U1 CS3351
[0091] Accordingly, each embodiment of the permanent magnet
alternator in accordance with the present invention is advantageous
over conventional designs in several respects. First, because the
alternator is physically smaller, it permits installation in
smaller spaces of an automobile or aircraft engine compartment. The
light-weight nature of the alternator is especially advantageous as
it pertains to the automotive and aerospace industries, whereby
fuel efficiency is closely related to the weight of the
vehicle/airplane. Moreover, because the alternator uses materials
that imparts a more robust structural design, the disclosed
alternator provides economic benefits by reducing repair costs and
promoting a longer service life.
[0092] Still further, the placement of fan projections on the side
surface of the rotor is advantageous in that it provides an overall
design that has both a high cooling capacity and reduced weight.
The use of the retaining shield is beneficial since it allows the
rotation of the rotor at high rpm without resulting in the
detachment of magnets from the rotor.
[0093] The use of permanent magnets yields several advantages in
terms of cost of construction, durability, and economic
feasibility. Moreover, the use of permanent magnets obviates the
need for slip rings or brushes in order to bring electrical power
into the rotational field element. Although the magnetic field
provided by a permanent magnet alternator is not controllable, the
invention achieves control of the system by using a voltage
regulator which controls the effective current supplied to a load.
The disclosed regulator circuit also provides a number of safety
control and failure condition indications to insure proper
operation of the system.
[0094] Although exemplary embodiments of the present invention have
been described in detail herein, it should be appreciated by those
skilled in the art that many modifications are possible without
materially departing from the spirit and scope of the teachings and
advantages which are described herein. Accordingly, all such
modifications are intended to be included within the spirit and
scope of the present invention.
* * * * *