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

Abstract

Wide band gap (WBG) devices are the latest trend in the power electronics industry. MOSFETs built using WBG materials offer numerous benefits to power electronic circuits. The benefit of using WBG MOSFETs over conventional Si IGBTs is the ability to operate at higher switching frequencies and lower dead times, which reduces the switching losses. This thesis will explore the application of WBG MOSFETs to motor drives, where higher switching frequencies reduce harmonic losses and torque ripple and allow higher control bandwidth, Two-level voltage source inverters (VSI) 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 times as well as high switching frequencies lead to increased shaft voltage and ground currents. Mitigation techniques of open-end winding drive and clamp-on ferrite chokes are evaluated in this thesis. The shaft voltage and ground currents are found to be eliminated when an open-end winding drive combines with the clamp-on ferrites. Simulation results of loss analysis is presented for a conventional two-level VSI and dual two-level VSI to understand the thermal requirements of the Si and SiC based drives. The advantages and disadvantages of WBG based conventional two-level inverter and the various mitigation techniques are discussed.