Development of Inverters with Forced Commutation for AC Motor Speed Control up to the Megawatt Range

The stages of development of inverters with forced commutation up to the megawatt range are described. The significant circuit designs such as capacitor turnoff, feedback diodes, and commutation inductances are already known from the mercury-arc and thyratron era. With the development of inverter-type thyristors today, inverters up to several hundred kilowatts can be realized for speed control of ac motors.