Combined starting/generating system and method

• US 4,481,459 A
• Filed: 12/20/1983
• Issued: 11/06/1984
• Est. Priority Date: 12/20/1983
• Status: Expired due to Fees

• Current Assignee: Sundstrand Corporation (Raytheon Technologies Corporation d/b/a RTX)
• Original Assignee: Sundstrand Corporation (Raytheon Technologies Corporation d/b/a RTX)
• Inventors: Mehl, Byron R., Glennon, Timothy F., Olson, Raymond N.
• Primary Examiner(s): Hickey, R. J.
• Application Number:
  US06/563,449
• Time in Patent Office: 322 Days
• Field of Search: 322/10, 322/11, 322/28, 322/29, 290/38 R, 290/46
• US Class Current: 322/10
• CPC Class Codes: F02N 11/04 the motors being associated with current generators
• CPC Class Codes: F02N 11/0859 specially adapted to the type of the starter motor or integrated into it
• CPC Class Codes: F02N 2011/0888 DC/DC converters
• CPC Class Codes: F02N 2011/0896 Inverters for electric machines, e.g. starter-generators
• CPC Class Codes: F02N 2200/041 Starter speed
• CPC Class Codes: H02P 2201/07 DC-DC step-up or step-down converter inserted between the power supply and the inverter supplying the motor, e.g. to control voltage source fluctuations, to vary the motor speed general aspects of plural converters in cascade H02M

Abstract

A power conversion system for converting between electric and motive power may be utilized either in a generating mode to generate electric power from motive power supplied by a prime mover or in a starting mode wherein motive power is developed by the power conversion system from electrical power and is supplied through a torque converter to the prime mover to start same. The power conversion system includes a main generator, an exciter and a permanent magnet generator, or PMG, which together comprise a brushless alternator. When operated in the starting mode, power is supplied to the PMG to cause it to act as a motor and thereby drive a rotor which is common to the PMG, exciter and main generator. Once a predetermined operating condition of the generator is attained, the main generator is supplied power from a motor control to cause the generator to act as a synchronous motor and the power supply to the PMG is disconnected. The torque converter is then commanded to transfer motive power from the generator to the prime mover to start same.

Claims

1. In a power conversion system operable in either a starting mode wherein the conversion system converts electrical power into motive power to start a prime mover or in a generating mode wherein the conversion system develops electrical power from motive power supplied by the prime mover including a main dynamoelectric machine, means actuable to supply field current to the main machine including a permanent magnet generator, or PMG, the main machine and PMG having a common rotor, and a torque converter operable to transfer power between the prime mover and the common rotor, a control for operating the conversion system in the starting mode, comprising:

a source of electrical power;

means for coupling the source of electrical power to the PMG when the conversion system is operated in the starting mode to cause the PMG to operate as a motor and drive the common rotor;

means coupled to the main machine for applying electrical power thereto to cause the main machine to operate as a synchronous motor when a predetermined operating condition of the main machine is attained;

means for disconnecting the source of electrical power from the PMG after the predetermined operating condition is attained; and

means coupled to the torque converter and responsive to an operating parameter of the main machine for controlling the torque converter including means for disabling the torque converter to decouple the main machine from the prime mover until the predetermined operating condition is attained and means for enabling the torque converter to couple the main machine to the prime mover to start the latter when the main machine is operated as the synchronous motor.

2. The control of claim 1, wherein the applying means includes means for sensing the speed of the common rotor and means for determining whether the speed of the common rotor has reached a first predetermined value.

3. The control of claim 2, wherein the speed sensing means includes a magnetic pick up, or MPU which develops pulses representing the rotation of the common rotor and means coupled to the MPU for deriving an indication of rotor speed from the MPU pulses.

4. The control of claim 3, wherein the deriving means includes means for indicating the length of time between successive MPU pulses.

5. The control of claim 4, wherein the deriving means further includes means coupled to the indicating means for computing rotor speed from successive indicated lengths of time.

6. The control of claim 4, wherein the deriving means further includes means coupled to the indicating means for computing rotor speed according to the equation ##EQU2## where:

K is a constant;

T₁ is the length of time between a first pair of successive MPU pulses; and

T₂ is the length of time between a second pair of successive MPU pulses.

7. The control of claim 1, further including means for selecting either the generating or starting modes of operation and means for initiating the generating mode when such mode is selected and the prime mover has started.

8. The control of claim 7, wherein the generating mode initiating means includes means for determining whether the speed of the common rotor has reached a second predetermined level and means for actuating the field current supply means after the second predetermined level is reached.

9. In a power conversion system selectively operable in either a starting mode wherein the conversion system converts electrical power into motive power to start a prime mover or in a generating mode wherein the conversion system develops electrical power from motive power supplied by the prime mover including a synchronous main dynamoelectric machine, means for providing field current to the main machine including a permanent magnet generator, or PMG, the main machine and PMG having a common rotor and a torque converter selectively actuable to transfer motive power between the prime mover and the common rotor, a control system for operating the conversion system, comprising:

means for selecting either the generating or starting modes of operation;

a source of electrical power; and

a control unit coupled to the selecting means and to the torque converter for operating the system in the selected mode, the control unit further including means for coupling the source of electrical power to the PMG to operate it as a motor to drive the common rotor when the starting mode is selected, means for deactuating the torque converter to allow the common rotor to rotate at increasing speeds in an unloaded condition, means for sensing the speed of the common rotor, means for applying electrical power to the main machine to operate it as a synchronous motor when the common rotor reaches a first predetermined level, means for disconnecting the source of electrical power from the PMG after the first predetermined level is reached and means for actuating the torque converter to cause motive power to be transferred from the main machine to the prime mover to start same when the main machine is operated as a synchronous motor.

10. The control system of claim 9, wherein the rotor speed sensing means includes a magnetic pick up, or MPU which develops output pulses in response to rotation of the common rotor, means for indicating the length of time between successive pulses and means for deriving an indication of rotor speed from the indicated length of time.

11. The control system of claim 10, wherein the deriving means includes means for computing the speed of the common rotor according to the equation ##EQU3## where:

K is a constant;

T₁ is the length of time between a first pair of successive MPU pulses; and

T₂ is the length of time between a second pair of successive MPU pulses.

12. The control system of claim 9, wherein the means for providing field current includes an exciter and wherein the control unit includes a voltage regulator coupled between the PMG and the exciter operable to deliver regulated voltage to the exciter and means for initiating the generating mode when such mode is selected and the prime mover has started including means for operating the voltage regulator whereby field current is delivered to the main machine so that the main machine develops electrical power.

13. The control system of claim 12, wherein the generating mode initiating means includes means for determining whether the speed of the common rotor has reached a second predetermined level and means for preventing operation of the voltage regulator until the second predetermined level is reached.

14. In a control process for a power conversion system operable in either a starting mode wherein the conversion system converts electrical power into motive power to start a prime mover or in a generating mode wherein the conversion system develops electrical power from motive power supplied by the prime mover including a main dynamoelectric machine, means actuable to supply field current to the main machine including a permanent magnet generator, or PMG, the main machine and PMG having a common rotor, and a torque converter operable to transfer power between the prime mover and the common rotor, an improved method of operating the conversion system in the starting mode, the method comprising:

disabling the torque converter to decouple the main machine from the prime mover;

coupling a source of electrical power to the PMG when the conversion system is operated in the starting mode to cause the PMG to operate as a motor and drive the common rotor;

applying electrical power to the main machine to cause the main machine to operate as a synchronous motor when the speed of the common rotor has reached a predetermined level;

disconnecting the source of electrical power from the PMG after the speed of the common rotor has reached the predetermined level; and

enabling the torque converter to cause motive power to be transferred from the main machine to the prime mover to start the latter when the main machine is operated as a synchronous motor.