Starter/generator system and method utilizing a low voltage source

An electric power starter/generator system for a turbine engine capable of transforming mechanical power from the turbine engine to electric power during a generate mode of operation and of transforming electric power from a low voltage dc source to mechanical power to drive the turbine engine during a start mode of operation, comprising:

• a synchronous starter/generator having a poly-phase wound stator, and a rotor rotatably positioned therein, said rotor being drivably coupled to the turbine engine;
• means for establishing an electric field in said rotor;
• means directly coupled to the dc source for alternately energizing each of said poly-phase stator windings to drive said starter/generator as a motor, said energizing means establishing a rotating electric field in said stator whereby a constant torque is produced by said rotor to drive the turbine engine;
• and
• wherein said energizing means comprises
• an inverter having an input directly coupled to the dc source, and a poly-phase output directly coupled to said poly-phase stator windings, said inverter having controllable switches responsive to drive signals for producing a stator excitation waveform,
• means for sensing rotor position, and
• means responsive to said rotor position for controlling said switches, said control means generating said drive signals to produce said stator excitation waveform to maintain said torque at a desired level;
• and
• wherein said inverter is a full wave inverter and wherein said stator excitation waveform is a poly-phase sinusoidal waveform.

An electric power starter/generator system for a turbine engine capable of transforming mechanical power from the turbine engine to electric power during a generate mode of operation and of transforming electric power from a low voltage dc source to mechanical power to drive the turbine engine during a start mode of operation, comprising:

• a synchronous starter/generator having a poly-phase wound stator, and a rotor rotatably positioned therein, said rotor being drivably coupled to the turbine engine;
• means for establishing an electric field in said rotor;
• and
• means directly coupled to the dc source for alternately energizing each of said poly-phase stator windings to drive said starter/generator as a motor, said energizing means establishing a rotating electric field in said stator whereby a constant torque is produced by said rotor to drive the turbine engine;
• wherein said energizing means comprises
• an inverter having an input directly coupled to the dc source, and a poly-phase output directly coupled to said poly-phase stator windings, said inverter having controllable switches responsive to drive signals for producing a stator excitation waveform,
• means for sensing rotor position, and
• means responsive to said rotor position for controlling said switches, said control means generating said drive signals to produce said stator excitation waveform to maintain said torque at a desired level;
• and
• wherein said inverter is a half wave inverter.

A method of driving a motor having a poly-phase wound stator, an exciter field, and a rotor rotatably positioned within the stator, the rotor being coupled by a shaft to a load, comprising the steps of:

• establishing field excitation;
• producing a poly-phase periodic half wave sinusoidal motor drive signal;
• scaling said motor drive signal by a scale factor;
• varying said scale factor during each period of said motor drive signal to produce a pseudo-square wave current waveform;
• and
• coupling said pseudo-square wave current waveform to the wound stator to drive the rotor to produce a constant torque.

An electric power starter/generator system for a turbine engine capable of transforming mechanical power from the turbine engine to electric power during a generate mode of operation and of transforming electric power from a low voltage dc source to mechanical power to drive the turbine engine during a start mode of operation, comprising:

• a synchronous starter/generator having a poly-phase wound stator, and a rotor rotatably positioned therein, said rotor being drivably coupled to the turbine engine;
• a voltage step-up transformer coupled to the dc source;
• means coupled to said step-up transformer for establishing an electric field in said rotor;
• and
• means coupled to said step-up transformer for alternately energizing each of said poly-phase stator windings to drive said starter/generator as a motor, said energizing means establishing a rotating electric field in said stator whereby a constant torque is produced by said rotor to drive the turbine engine.

An electric power starter/generator system for a turbine engine capable of transforming mechanical power from the turbine engine to electric power during a generate mode of operation and of transforming electric power from a low voltage dc source to mechanical power to drive the turbine engine during a start mode of operation, comprising;

• a synchronous starter/generator having a poly-phase wound stator, and a rotor rotatably positioned therein, said rotor being drivably coupled to the turbine engine;
• a voltage step-up transformer coupled to the dc source;
• means coupled to said step-up transformer for establishing an electric field in said rotor;
• means coupled to said step-up transformer for alternately energizing each of said poly-phase stator windings to drive said starter/generator as a motor, said energizing means establishing a rotating electric field in said stator whereby a constant torque is produced by said rotor to drive the turbine engine;
• wherein said energizing means comprises
• a half wave inverter having an input coupled by a first and a second rectifying diode to said voltage step-up transformer, and a poly-phase output directly coupled to said poly-phase stator windings, said inverter having controllable switches responsive to drive signals for producing a stator excitation waveform,
• means for sensing rotor position, and
• means responsive to said rotor position for controlling said switches, said control means generating said drive signals to produce said stator excitation waveform to maintain said torque at a desired level;
• and
• wherein said stator excitation waveform produced by said half wave inverter departs from a normal half sine wave by a variable scale factor to maintain a constant torque.