Mitigation of motor overvoltage in SiC-based drives using soft-switching voltage slew-rate (dv/dt) profiling

In silicon carbide (SiC) device based motor drives, the high voltage slew rate (dv/dt) associated with the fast switching transitions results in excessive motor overvoltage, due to the reflected wave phenomenon, which increases the motor winding insulation stress and causes premature failure while raises electromagnetic interference (EMI) problems. This article proposes a voltage slew rate profiling approach to mitigate the motor overvoltage in SiC-based cable-fed drives. The proposed approach optimizes the rise/fall time of the output voltage according to the cable length, without altering the switching speed of the SiC devices. The proposed profiling approach is implemented using a soft-switching inverter. The optimum rise/fall time that can significantly mitigate the overvoltage is derived using frequency and time domain analysis. The auxiliary resonant commutated pole inverter (ARCPI) is adopted as a soft-switching inverter to experimentally verify the proposed slew rate profiling approach for the overvoltage mitigation. The analysis and experimental results show that the motor overvoltage is fully mitigated when the output voltage rise/fall time is set as the cable anti-resonance period, i.e. four times of the wave transmission time along the cable. Further, the slew-rate profiling approach along with the ARCPI reduces the switching loss and improve the EMI performance at high frequency region.