Starter-generator utilizing phase controlled rectifiers to drive a dynamoelectric machine as a brushless DC motor in the starting mode with starter position sense variation with speed

In a starter-generator system, the combination of:

• a. a dynamoelectric machine for operation both as a brushless DC motor and as a constant frequency AC generator,
• b. cycloconverter means coupled to said machine for selectively supplying current to the machine armature windings during motoring operation and for converting the frequency of the output signal from the machine to provide a constant frequency output during generator operation, said cycloconverter means including banks of oppositely poled, phase controlled, gated, switching devices.
• c. means to operate said dynamoelectric machine as a brushless DC motor including,
• 1. a source of constant frequency alternating supply voltage coupled to said banks of switching devices,
• 2. means for sensing the rotor position of said dynamoelectric machine and for producing in response thereto enabling signals to gate selected ones of said switching devices in sequence to permit current flow in selected armature windings as a function of rotor position so that current flows in the armature winding having flux associated therewith to produce positive torque,
• 3. means for controlling the phase angle between armature current, flux, and machine voltage over a predetermined speed range only to provide a fixed phase angle over a speed range wherein the machine voltage frequency does not exceed one-half of the supply voltage and to vary the phase angle at speeds wherein the machine voltage frequency exceeds one-half the supply voltage frequency, including means responsive to the speed of the machine for shifting the phase of the enabling signals to vary the angle at which the switching devices are gated over the speed range wherein the machine voltage frequency exceeds one-half of the supply voltage frequency, to permit commutation of the switching devices by the machine voltage whereby the said gating angle is maintained at a fixed minimum value at speeds up to said range thereby maximizing torque, and is increased with speed over said speed range,
• d. a source of constant frequency reference waves,
• e. means for converting the system from the motoring to the generating mode including means responsive to the speed of the dymamoelectric machine for disconnecting the constant frequency supply voltage, and for disconnecting the rotor position sensing and enabling signal producing means from said bank of switching devices when the machine reaches a predetermined speed at which the machine is to operate as a generator, and means for coupling the source of constant reference frequency waves to said banks of said switching devices for said cycloconverter means when the machine reaches said predetermined speed.