Experimental Verification of Current-Source Inverter With ZVS Commutation Circuit

This paper presents a current-source inverter suitable for high-voltage/high-power motor drives. This inverter uses thyristors as main switching devices and utilizes a zero-voltage-switching (ZVS) commutation circuit. It has the advantages of good motor power factor and self-startability. We have evaluated a test model of the proposed inverter and a motor and verified that the inverter operates at a motor power factor of one and that it can be started even when the motor speed is zero. Moreover, a six-phase synchronous motor was driven by two of these inverters; it was confirmed that they decreased the motor torque ripple and the harmonic component of the voltage source. In addition, we evaluated the operation of the ZVS commutation circuit by simulation and experiment and thus verified that turnoff loss depends mainly on the inductance of the ZVS commutation circuit and not on gate resistance. Moreover, when the switching device turns off the current, its voltage is almost zero. That is, even if the inductance is large, the peak voltage of the switching device is low and switching loss is small. Therefore, the ZVS commutation circuit can be easily composed because it does not need to be of low inductance. These results show that a large-capacity drive system can be easily achieved with the proposed inverter.