U.S. patent number RE29,579 [Application Number 05/716,325] was granted by the patent office on 1978-03-14 for dual source auxiliary power supply.
This patent grant is currently assigned to General Electric Co.. Invention is credited to Martin Simon.
United States Patent |
RE29,579 |
Simon |
March 14, 1978 |
Dual source auxiliary power supply
Abstract
An auxiliary power supply system for providing controlled
alternating current in an electric motor traction vehicle driven by
a prime mover through a traction alternator. During normal traction
operation the prime mover operates at a high constant rotational
speed to directly drive an auxiliary alternator which provides the
auxiliary power, while in standby operation the prime mover
operates at a reduced constant rotational speed and the auxiliary
power is obtained from the traction alternator at the desired
frequency and voltage.
Inventors: |
Simon; Martin (Erie, PA) |
Assignee: |
General Electric Co. (Erie,
PA)
|
Family
ID: |
22722649 |
Appl.
No.: |
05/716,325 |
Filed: |
August 20, 1976 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
Reissue of: |
195753 |
Nov 4, 1971 |
03745366 |
Jul 10, 1973 |
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Current U.S.
Class: |
307/68 |
Current CPC
Class: |
B60L
50/12 (20190201); H02P 9/34 (20130101); Y02T
10/70 (20130101); B60L 2200/26 (20130101); Y02T
10/7072 (20130101); Y02T 10/64 (20130101) |
Current International
Class: |
B60L
11/06 (20060101); B60L 11/02 (20060101); H02P
9/34 (20060101); H02P 9/14 (20060101); H02J
009/04 () |
Field of
Search: |
;307/47,66,67,68,80,81,84 ;290/11,17 ;180/65 ;105/35,61,62 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Schaefer; Robert K.
Assistant Examiner: Indyk; Eugene S.
Attorney, Agent or Firm: Beusse; James H.
Claims
What I claim as new and desire to secure by Letters Patent of the
United States are:
1. In a traction vehicle of the type wherein thermal prime mover
means drives a traction alternator having a predetermined number of
.[.commutating.]. poles and adapted to energize traction motor
means, an auxiliary power arrangement adapted to produce
alternating current, the combination comprising:
a. an auxiliary alternator having a plurality of .[.commutating.].
poles .[.greater.]. .Iadd.less .Iaddend.than the number of poles of
said traction alternator;
b. means for mechanically coupling said prime mover means to said
auxiliary alternator;
c. governor control means for maintaining the shaft speed of said
prime mover at a first predetermined shaft speed during normal
operation of said traction vehicle and at a second predetermined
reduced speed during standby operation of the traction vehicle;
d. an alternating current circuit having an output adapted to
energize auxiliary power circuits and an input;
e. switching means to connect said input to the output of said
auxiliary alternator during normal operation of said traction
vehicle, and to connect said input to the output of said traction
alternator during standby operation of said traction vehicle;
f. wherein the number of .[.commutating.]. poles of said auxiliary
alternator is substantially equal to the product of the number of
.[.commutating.]. poles of said traction alternator and the ratio
of said .[.first.]. .Iadd.second .Iaddend.predetermined shaft speed
to said .[.second.]. .Iadd.first .Iaddend.predetermined shaft
speed.
2. The auxiliary power source of claim 1 and including control
means having an input connected to be responsive to the traction
power applied to said traction motors and an output connected to
regulate the excitation of said traction alternator, wherein during
standby operation of said vehicle, said control means is connected
to be responsive to the output of said alternating current
circuit.
3. A traction vehicle propulsion system as defined in claim 2
wherein said control means is effected by a reference current, said
reference current during normal operation being variably responsive
to said governor control means and during standby operation being a
constant current of .[.of.]. a predetermined magnitude.
Description
BACKGROUND OF THE INVENTION
This invention relates generally to electrical power supply systems
for electrically propelled traction vehicles and more particularly
to alternating current auxiliary power supply systems utilized in
electrically propelled vehicles, wherein alternating current
generating means, driven by a thermal prime mover, energizes the
propulsion motors of the vehicle.
Traction vehicles, such as diesel electric locomotives, commonly
utilize a thermal prime mover to drive a traction alternator whose
output provides electrical power to the traction motors. The prime
mover, such as a diesel engine or the like is operated at various
speeds by throttle control in accordance with the power
requirements of the alternator.
In addition to traction power, it has also been necessary to
provide auxiliary power for lighting, heating and air conditioning.
Frequently, it is desirable to provide alternating current
auxiliary power for this purpose. Historically, this power has been
provided by an auxiliary alternator which is driven by an auxiliary
prime mover at a constant rotational speed to ensure an auxiliary
power supply of constant frequency and voltage. The auxiliary prime
mover and alternator are thus operated continuously to provide the
required power both during periods of normal traction operation and
during standby operation, wherein the vehicle is standing idle as
when awaiting call. During standby, auxiliary power is required,
but to a much lesser extent than when in normal traction operation.
This varying of the load on the auxiliary prime mover, which has
traditionally been a diesel engine, causes considerable problems in
maintenance with attendant costs. The expense of an extra diesel
engine is thus substantial when considering original installation
costs and subsequent overhaul demands.
It is therefore desirable to eliminate the auxiliary prime mover
and to drive the auxiliary alternator directly from the traction
prime mover which has sufficient available power. However, in
conventional diesel electric vehicles the speed of the prime mover
is varied during operation, by changing the setting of the throttle
lever. This variation of prime mover speed would result in a change
in auxiliary alternator speed with a corresponding change in output
voltage and frequency.
Energization of the auxiliary power source by the prime mover is
further complicated because of standby operation of the vehicle.
During time periods wherein the vehicle is in a standby condition,
the auxiliary power is still required, but the traction power is
not, and thus the operation of the prime mover at the constant high
speed is impractical. The resulting noise in residential areas is
extremely undesirable. A reduction in prime mover speed will reduce
the noise level, but would in turn excessively reduce the frequency
of the auxiliary alternator. The use of gears to maintain the
alternator speed while slowing the prime mover speed would involve
unnecessary expense and difficulty.
It is therefore an object of this invention to provide an improved
system for generating alternating current of substantially uniform
frequency, for use as auxiliary power in a traction vehicle wherein
alternating current generating means driven by prime .[.moving.].
.Iadd.mover .Iaddend.means energizes propulsion motors.
It is another object of this invention to attain the aforesaid
arrangement without requiring a prime mover additional to the prime
.[.moving.]. .Iadd.mover .Iaddend.means otherwise required to drive
the propulsion alternating current generating means.
Yet another object of this invention is to provide an improved
alternating current auxiliary power source providing substantially
constant frequency and output voltage during periods of normal and
standby operation of the vehicle.
Still another object of this invention is to achieve the aforesaid
objectives without complex gearing and with use of components of
the propulsion system of the traction vehicle.
A further object of this invention is to minimize the noise level
of a traction vehicle operating in a standby condition.
SUMMARY OF THE INVENTION
The invention relates to an auxiliary power supply system utilizing
a prime mover-driven, auxiliary alternator to provide polyphase
power of predetermined voltage and frequency during normal traction
operation, and utilizing the main-drive traction alternator to
provide auxiliary power during standby operation, wherein the prime
mover is operated at a considerably reduced speed. The system is
amplifier controlled, and provides for voltage and current limits
in both modes of operation.
In the drawings as hereinafter described a preferred embodiment is
depicted; however, various other modification and alternate
constructions can be made thereto without departing from the true
spirit and scope of the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a simplified block diagram illustration of a traction
vehicle power system showing the incorporated invention in dashed
lines.
.[.FIG. 2.]. .Iadd.FIGS. 2a and 2b .Iaddend.is a simplified
schematic circuit diagram of a preferred embodiment of the
system.
FIG. 3 is a simplified schematic circuit diagram of the voltage
regulator and auxiliary alternator excitation portion of the
preferred embodiment.
DESCRIPTION OF THE PREFERRED EMBODIMENT
Reference is now made to FIG. 1. A thermal prime mover 11 such as a
diesel engine has its output shaft 12 coupled to drive the traction
alternator 13 whose output 14 passes through the rectifier 16 and
lines 17 to energize the traction motors 18. Field current for the
traction alternator is supplied by lines 19 from an exciter 21
whose input power is supplied by lines 22 from an excitation
circuit 23. Adjustment of the throttle position 24 varies the input
26 to the excitation circuit, thus controlling the field current to
the traction alternator and hence the load imposed on the prime
mover. Accordingly, the output of the traction alternator is varied
by changing the field current 19 through the excitation circuit 23.
A governor 15 is operably connected to the diesel engine to control
its speed at substantially a constant rotational rate.
A prime mover of the diesel engine type characteristically tends to
deliver constant power output for a given diesel engine operating
speed. Variations in the diesel engine speed result in variations
of diesel output power. For reasons hereinafter discussed, it is
desirable for certain traction vehicles such as those used on
commuter trains, to operate the prime mover at a constant rate of
speed regardless of the load.
The power output of the traction alternator is controlled to
prevent excessive voltages and currents and additionally to prevent
the power requirements of the traction alternator from exceeding
the available power output of the diesel engine. Thus, limiting the
electrical horsepower requirements of the traction alternator to
the available horsepower output of the diesel engine substantially
decreases diesel engine wear and avoids diesel engine speed
variations and stalling. This limiting action is achieved by a
control system wherein voltage and current feedback signals are
applied from the line 17 through voltage feedback circuit 25 and
current feedback circuit 27 to the comparison circuit 30. The
output of the comparison circuit is coupled to the excitation
circuit 23 through leads 35 for regulating the excitation and thus
the power output of the traction alternator.
The above described arrangement is well-known in the art (for
example, in the pending application Ser. No.
.Badd..[.859,848.]..Baddend. .Iadd.850,848 .Iaddend.filed Aug. 18,
1969, of Thomas L. Vandervort, .Iadd.now U.S. Pat. No. 3,621,370
.Iaddend.and assigned to the assignee of this application).
Traction vehicles such as commuter trains or the like require, in
addition to traction power, an auxiliary power system to be
provided for the auxiliary machinery used for lighting, heating,
and air conditioning of the cars. The power generally required is
of the a-c type having a controlled voltage and frequency. During
normal operation auxiliary power is provided by an auxiliary
alternator 29 driven by the prime mover 11 through a coupling means
31, such as a drive shaft or the like. The constant speed operation
of the prime mover during normal operation permits direct
mechanical coupling of the auxiliary alternator to the prime mover,
thus obviating the separate prime mover in order to maintain a
constant power frequency. The output 32 from the auxiliary
alternator is applied through power transfer switch 41 to an
auxiliary power output circuit, i.e. the trainline 33, for driving
the auxiliary machinery. In a preferred embodiment the output is
512 volts at 64 Hz. As previously stated, the prime mover is
operated at a constant rotational speed, which include preferred
embodiment is 960 rpm, and hence, the auxiliary alternator is also
operated at a constant speed, thus ensuring a constant frequency
power supply to the trainline. The voltage appearing across the
line 32 is applied by the line 34 to a voltage regulator 36. The
output of the voltage regulation is directed along line 37 to the
auxiliary alternator 29 for which it provides a field current.
A current feedback circuit 44, hereinafter described is provided
principally for standby operation wherein the current feedback
circuit 27 is open circuited.
A current limiter 38 may be interconnected between the current
feedback circuit 44 and the voltage regulator 36 for use during
normal operation.
Because of the necessity for maintaining an auxiliary power output
for providing heating and cooling during standby operation, it is
necessary to maintain operation of a prime mover during this
period. However, while continued operation of the diesel engine and
regulated output of auxiliary power is required, there is generally
a need to reduce the noise level of the prime mover. This noise
level is reduced by reducing the speed of the prime mover, and if
the speed is reduced and held to a fixed predetermined speed, it
will permit use of the main alternator to provide the auxiliary
power of constant frequency, thereby eliminating the need for an
auxiliary prime mover.
During time periods wherein the traction vehicle is in a standby
condition, such as when standing in the yard at night, the power
transfer switch 41 is thrown, thereby disconnecting the output of
the auxiliary alternator and connecting the output of the traction
alternator through line 42 (indicated by a dashed line in FIG. 1).
During this period of operation, the prime mover operates at a
reduced constant rotational speed, for example 600 rpm, and the
auxiliary power to the trainline is obtained from the traction
alternator output 14, a typical output being 480 volts at 60 Hz, as
shown in FIG. 1. In a standby condition, the traction alternator
field is controlled so as to maintain the appropriate auxiliary
voltage and to limit output current to a predetermined magnitude.
The current feedback circuit 44 sends current feedback signals from
the traction alternator output to the comparison circuit, thereby
controlling the amount of current being delivered to the line 42 in
a manner discussed hereinafter. During standby operation the
voltage feedback circuit 25 continues to function, but the current
feedback circuit 27, which is responsive to current being delivered
to the traction motors 18 is rendered inactive by the switch
assembly 28.
The auxiliary power frequency should be maintained within a
reasonable range such as .+-. 12 percent. Frequency output of
auxiliary power during standby and normal operation is maintained
within that range by appropriate selection of poles of the
auxiliary alternator vs. poles of traction alternator. Since the
frequency of an alternator. in Hz, is related to the number of
poles and the speed, as expressed by the equation
f.[.=.]..Iadd..varies..Iaddend. (number of poles) X (speed), the
auxiliary alternator is selected to have a number of poles
approximately represented by the equation
(number of poles of .Iadd.auxiliary .Iaddend.alternator) = [(RPM
standby)/(RPM normal)](Number of poles of traction .[.motor.].
.Iadd.alternator.Iaddend.)
An 8 pole, 3 phase auxiliary generator operating at 960 rpm will
have a 64 Hz, 512 volt output, whereas a 12 pole, 3 phase, traction
alternator operating at 600 rpm will produce a 60 Hz, 480 volt
output. Accordingly, the speed of the traction alternator is
reduced from 960 rpm to 600 rpm when changing from normal traction
operation to standby operation. Thus, an output may be obtained
from the traction alternator operating at low speeds which has
nearly the same characteristics as the output of the auxiliary
alternator operating at higher speeds.
Referring now to FIG. 2, the control circuitry of a preferred
embodiment is illustrated in partial schematic form and includes in
greater detail, the excitation circuit 23, and the comparison
circuit 30 (indicated by dashed line boxes) with the corresponding
voltage feedback circuit 25 and the current feedback circuits 27
and 44, as well as the relative placement of the contacts of the
power transfer switch 41.
The traction alternator 13, which is driven by the prime mover 11,
provides three-phase power to leads 14. During normal traction
operation of the vehicle the current passes through the rectifiers
16 and hence to the traction motors 18 for driving the vehicle.
Provided in the propulsion circuit is a current limit and voltage
limit arrangement responsive to the propulsion current feedback
circuit 27 and the propulsion voltage feedback circuit 25
respectively. The propulsion current limit is maintained by an ACCR
.Iadd.(armature current control reactor) .Iaddend.reactor 61 which
is responsive to the current flow through a shunt 48 placed in the
flow of the drive current. The shunt 48 which is adapted to receive
a large current and passes a representative current through lines
46 to the reaction control winding 47 which is responsive to limit
the current flow in the circuit as will be hereinafter described.
The propulsion voltage limitation is provided by applying a voltage
feedback control signal to the traction alternator exciter 21. The
output of the rectifiers 16 is coupled by lines 17 and 51 to the
control winding 47 of the VCR .Iadd.(voltage control reactor)
.Iaddend.62. The resistor 49 in series circuit therewith limits the
feedback current. Voltage and current control circuits are
well-known in the art as shown by the description in the referenced
Vandervort application.
Reference is now made to the control portion of the system which
includes the comparison circuit 30 and the excitation circuit 23,
each identified in FIG. 2 by a dashed line box.
COMPARISON CIRCUIT
The comparison circuit is of the type described in the previously
referenced Vandervort application and includes two bridge rectifier
circuits 58 and 59 and associated current and voltage measuring
reactors, 61 and 62 respectively. The outputs of the rectifier
bridges are serially connected across a unidirectionally conducting
output comparison circuit 30. This comprises in series circuit,
first output circuit terminal 73, line 74, rectifier bridge 58,
line 76, rectifier bridge 59, line 77 and second output terminal
78. The output circuit, connected to terminals 73 and 78 comprises
serially connected line 70, the primary winding of a pulse width
modulator 79, a rectifier 81 and line 82. The rectifier 81 is poled
to permit the conduction of the rectified feedback current through
the output circuit.
The reference current entering the first output circuit terminal 73
through line 83 is supplied from two different sources depending on
whether the vehicle is operating in a normal traction mode or
whether it is operating in a standby condition. In the normal
operating condition the reference current is supplied from a
circuit comprising a d-c power source 84 connected across line 86
and 87, with a locomotive throttle potentiometer 88 whose arm
movement is controlled by the locomotive throttle 24, diesel engine
governor load control potentiometer 89, and a dropping resistor 91
connected serially between terminal 90 and 100 and lines 86 and 87
respectively. Also, connected between lines 86 and 87 are the
serially connected resistors 92 and 93, the resistor 92 having a
substantially greater resistance than that of resistor 93. The
actual reference current then flows through a circuit serially
comprising the governor control 89, line 94, resistor 96 power
transfer switch 41b, line 83, the comparison circuit 30, line 97,
power transfer switch 41c, line 98, resistor 93, line 87, power
source 84, line 86, terminal 90, throttle 88 and line 99 to the
governor. As the throttle is opened, the resistance is decreased
and the reference current to the comparison circuit is increased,
thereby providing a greater current and voltage limit. Similarly,
the setting of the governor load control, and hence its resistance
value, is a function of the capability of the diesel engine. The
governor load control circuit has as its function to correct any
momentary reductions of engine speed by unloading the prime mover.
Accordingly, during normal operation the resistance is at a
minimum, while at time of overloading the engine speed is reduced,
the resistance of the governor control is increased, and the
reference current, and hence the voltage and current limit are
reduced.
The current signal in line 70 enters the excitation panel 23
through a PWM .Iadd.(pulse width modulation) .Iaddend.winding 79.
The excitation panel comprises a pulse width modulator 106, a power
transistor bridge circuit 107, and an exciter coil 108. The pulse
width modulator which is electrically connected across the d-c
power source 84 at terminals 109 and 111, has an outlet line 112
which carries an amplified signal to the base of a power transistor
113 of the bridge circuit 107. The bridge circuit has input
terminals 107a and 107b and output terminals 107c and 107d, the
input terminals being connected across the d-c power source by
leads 114 and 116, and the output terminals having connected
therebetween the exciter coil 108. The NPN power transistor is
connected between the terminals 107b and 107d with its emitter
nearest the terminal 107b. Connected in the other legs of the
bridge circuit are the resistors 117, 118 and 119 connected between
terminals 107d and 107a, 107a and 107c, and 107c and 107b,
respectively. The PWN is a self-saturating reactor with a main a-c
winding and several d-c control windings. The a-c winding is
connected from one output of an oscillator to the power transistor,
and the d-c windings are connected to line 70. The oscillator
provides a square wave a-c to turn the transistor off and on at
approximately 800 times a second. The PWM responds to the feedback
signals in line 70 and causes the transistor to turn off and on in
response thereto, the ratio of off to on time being determined by
the power demand and varied accordingly by the signals from the
ACCR and VCR. The exciter field is thus fed from the vehicle
battery in relation to the transistor on and off control, and the
alternator output is varied accordingly.
During normal operation of the traction vehicle, the auxiliary
alternator 29, driven by the prime mover at a constant speed
through coupling 31, provides three-phase current through its
output leads 32 to the trainline 33, and through the power transfer
switch contacts 41(a) which are set in the indicated position.
Voltage limitation is provided wherein voltage feedback signals
pass through leads 34 to the input of voltage regulator 36. In the
voltage feedback system the leg having the highest voltage is used
to generate a limiting signal. The voltage regulator applies one of
the three line-to-line voltages to an excitation control circuit 20
which provides a d-c current to the field winding circuit 35.
Various known circuits may be used to accomplish this regulation,
FIG. 3 shows one arrangement which is commonly used in the art and
includes a bridge rectifier 39, voltage measuring means 40, and an
a-c power source 56. The bridge rectifier 39, is connected to legs
34a and 34b at its terminals 39a and 39b. The alternating inputs
from these legs is rectified to enter line 57 through the output
terminal 39d. A d-c current is thus provided to the field winding
35 and returns along line 65 to the rectifier input terminal 39c.
The a-c power supply 56, such as a chopper or oscillator or the
like, is responsive to the voltage measuring means 40 to increase
or decrease the flow of current to the exciter field winding 35.
The output of the auxiliary alternator 29 is thus voltage
regulated. Locomotive battery current from the d-c source 84 is
provided by lines 55 and 60 to supply the field current for the
initial alternator build-up. The switches 125a and 125b are
actuated and displaced from the positions shown in FIG. 3 during
initial build-up, and are returned to their indicated positions by
relays when sufficient current is being provided by the alternator
29 to maintain the field. The current being delivered to the
trainline is limited by a conventional current limiter circuit 38
which receives current feedback signals through an ammeter 75 from
the current transformers 53 connected to the respective legs of the
three-phase output. A rectifier 80 is connected to the output of
the current limiter to provide a d-c signal to the current control
winding 95 along lines 45.
During periods of standby operation, wherein the traction
alternator is providing auxiliary power, the drive switches 105 are
opened thereby opening the circuits to the traction motors and to
the current feedback shunt 48. Similarly, the power transfer switch
is actuated and contacts 41b and 41c as well as 41(a) are actuated
and displaced from the position shown in FIG. 2 thereby connecting
terminals 101, 102 and 103 respectively. The reference current then
is a constant current signal coming from the voltage regulator 36
through line 104, which current is directed through the comparison
circuit 30 to the terminal 102 through the line 106, to line 87,
the power source 84, line 86, terminal 90 and hence back to the
voltage regulator 36. The reference current is provided to line 104
from a constant current source 115 which is connected to the
vehicle battery 84, across the lines 55 and 60. This constant
current source is obtained by conventional circuitry and its output
value is appropriately chosen to be equal to the current that flows
through the VCR 62 when a specified voltage appears at the output
of the traction alternator, (for example, 21 milliamps when the
voltage is 480 volts). Similarly, the rectified current feedback in
the circuit 44 is adjusted in amplitude by resistors 120 so as to
obtain the desired milliamp/volt relationship, wherein when the
current being delivered to the trainline reaches a specific
predetermined level the ACCR will generate the proper signal to
reduce the excitation to the traction alternator, thereby limiting
the trainline current to the desired level.
As previously discussed, during normal traction operation, a
voltage feedback signal originates at the rectified portion of the
traction circuit and is applied by line 25 to the control winding
47 of the voltage measuring reactor 62. During standby operation,
this feedback signal continues to be applied from the rectifiers
16. Thus, a voltage limit control is maintained in the same manner
as in normal operation.
As stated hereinbefore, current limit control during normal
operation is maintained through the control winding 47. However,
during periods of standby operation, the opening of the drive
switches acts to switch out the shunt 48 and hence the reaction
control winding 48. It is necessary, therefore to provide another
current feedback circuit when the power transfer switch contacts
41d are closed. When a circuit is provided for a current feedback
signal to enter from the voltage regulator, along line 45, to the
control winding 95 whose signal changes the primary winding
impedance and hence modulates the a-c signal from the supply
71.
The current feedback signal output of the current measuring reactor
61 is thus applied to the bridge rectifier 58 and the voltage
feedback signal output of the VCR 62 is applied to the bridge
rectifier 59. The output of the bridge rectifiers are connected
serially by lines 83, 76 and 77 in the reference current circuit.
Accordingly, a comparison is effected between the reference current
and the voltage or current feedback signal having the larger
magnitude. If the voltage and/or current feedback signals exceed
the reference current signal in magnitude, a current signal
proportional to the difference between the greater one of the
feedback signals and the reference current, is applied to the PWM
winding through line 70, which PWM winding responds thereto by
causing a reduction in excitation to the traction alternator and
thus a reduction in voltage. This arrangement limits the maximum
voltage and current outputs of the traction generator in reference
to current and voltage being delivered to the auxiliary machinery.
The excitation circuit is one such as is commonly used in the art
and is not considered to be unique. The embodiment which is
hereinafter described represents only one manner of controlling the
excitation to the traction alternator.
* * * * *