Patent US 5,029,263

The problem of providing aircraft engine starting is solved with an engine start control apparatus operating a generator (12) as a synchronous motor. The motor (12) receives power from a main inverter (46) and an excitation inverter (48) through an exciter (14) operating as a rotary transformer. These inverters (46, 48) are controlled by a control unit (22) which provides for constant power characteristics in the field weakening range. The control unit (22) includes a pulse width modulation (PWM) generator (100) which is responsive to a voltage command (102) and a commutation command (104) to develop switching signals (88) for controlling the switches (S1-S6) in the main inverter (46). The voltage command (102) is used to vary the duty cycle of the PWM signals. The commutation angle command (104) is used to control the timing of the PWM signals. The voltage command (102) and the commutation angle command (104) are controlled using closed loop current control.