Variable frequency SCR inverter with an auxiliary commutation circuit

With the recent development of static inverters using thyristors (silicon controlled rectifiers), many extensive attempts have been made to use them as adjustable frequency sources with the aim of realizing simple and accurate speed control systems of ac motors. For these applications, we have developed the improved inverter which has an auxiliary commutation circuit and a feedback current transformer. The auxiliary commutation circuit functions to improve the commutation characteristics and operation reliability, while the feedback current transformer improves the efficiency and stability. The distinguished characteristics of this new inverter have been proved by the experimental drives of induction motors and synchronous motors in wide frequency ranges.