Mitigation of uneven surge voltage stress on stator windings of induction motors fed by SiC-MOSFET-based adjustable speed drives

Power inverters based on wide bandgap (WBG) switching devices are being increasingly applied in new-generation adjustable speed drives (ASDs), due to their benefits of high efficiency and high power density. However, the high change rate of the output voltage (dv/dt) generated from the fast switching operation of the WBG devices in ASDs, such as Silicon Carbide (SiC) MOSFETs, could cause significant surge voltages which will be unevenly distributed in the motor windings, especially in the first coil of the stator windings. This paper will investigate various approaches to mitigate the surge voltage stress on the stator windings of a 5-hp induction motor, which is driven by a SiC-MSOFET-based ASD prototype. Simulation and experimental results verify that the stress of surge voltage and dv/dt on the first few turns of the first coil is much higher than these on other winding turns, which can be mitigated by three effective approaches, including using multilevel inverter, dv/dt filter, and integrated motor drive techniques.