Mitigation of Common-mode Noise in Wide Band Gap Device Based Motor Drives

MOSFETs built using wide band gap (WBG) materials offer numerous benefits to power electronic circuits. These benefits are quite apparent in applications requiring breakdown voltages >= 600 V, where Silicon IGBTs are typically used due to their combination of high breakdown voltage and low conduction losses. Compared to Silicon IGBTs, WBG MOSFETs offer very short turn-ON and turn-OFF times, which reduce switching losses and enable significantly higher switching frequencies. This paper explores the application of WBG MOSFETs to motor drives, where higher switching frequencies reduce motor losses and torque ripple and allow higher control bandwidth, thus enabling greater output frequencies needed to operate motors at higher speeds. Specifically, two-level voltage source inverters utilizing Silicon Carbide (SiC) MOSFETs are constructed to operate a 1 HP induction motor. Experimental results are presented which show that the short turn-ON and turn-OFF transients as well as high switching frequencies lead to increased shaft voltage and conducted ground currents. Mitigation techniques are implemented and evaluated, including clamp-on ferrites and an open-end winding drive implementation. The shaft voltage and ground currents are found to be best suppressed in an open-end winding drive utilizing clamp-on ferrites.