Phase locking of switching-transistor converters for polyphase power supplies

SWITCHING transistors may be used in conjunction with saturable-core output transformers to convert direct-voltage inputs into alternating voltages of nearly rectangular wave form.1 The output impedance is low, the over-all conversion efficiency is high, and (even in the present state of power-transistor development) output powers of tens of watts are available. Such transistor converters are therefore being considered as supply sources for magnetic amplifiers, a-c servomotors and other components used in low power servocontrol systems. For example, in air-borne military applications, transistor power supplies may replace small rotating machine inverters, which at present produce 400-cycle-persecond supplies from the aircraft battery system, with advantages in reliability and weight.