Mitigation of Motor Overvoltage in SiC-Device-Based Drives using a Soft-Switching Inverter

In SiC motor drives, the high-voltage slew rate (dv/dt) of switching transients results in excessive motor overvoltage, due to the reflected wave phenomenon (RWP), which stands behind the premature failure of motor winding insulation while raises electromagnetic interference (EMI) problems. This paper adopts a soft-switching inverter topology, denoted as the auxiliary resonant commutated pole inverter (ARCPI), to mitigate the motor overvoltage caused by the RWP in SiC-based cable-fed drives. The performance of the SiC motor drive system under the RWP is first investigated to determine how the motor overvoltage is affected by the dv/dt. of the inverter output voltage and the cable length. Then, a SiC ARCPI with profiled output voltage slew rate is utilized as a candidate solution to mitigate the RWP in the cable-fed motor drive. The effectiveness of the presented mitigation approach is experimentally verified, where it is shown that the ARCPI can completely eliminate the motor overvoltage and improve the EMI performance at high frequency region (500 kHz onwards) due to the prolonged rise/fall time of the output voltage, compared with the conventional hard-switching inverter.