Abstract: An inverter circuit includes fast transistors for PWM and slow switching thyristors for a fundamental frequency. The inverter circuit further includes a rectifying circuit for rectifying an input AC power and a bridge circuit. The bridge circuit includes a plurality of bridge circuit arms, each of the bridge circuit arms constituted by connecting a collector terminal of a transistor to a cathode terminal of a thyristor. An emitter of the transistor is connected to a negative side of the rectified output of the rectifying circuit, and an anode of the thyristor is connected to a positive side of the rectified output of the rectifying circuit.

Abstract: An electric circuit for supplying electrical power having a controlled frequency to a load includes thyristors, each having an anode terminal, a cathode terminal, and a gate terminal for supplying an electric current from the anode terminal to the cathode terminal; transistors, each having a collector terminal, an emitter terminal and a base terminal for switching ON/OFF an electric current from the collector terminal to the emitter terminal; an arm device connected between the cathode terminal of the thyristor and the collector of the transistor; bridge circuit device, having a plurality of arms between one terminal and another terminal of an electrical power source, so that the positive terminal is coupled to the anode terminal of the thyristors and the negative terminal is coupled to the emitter terminal of the transistor, and controlling circuit, connected to the load, for supplying an electric signal to the base terminal of the transistor to apply an electric voltage intermittently to the load, and suppl