SiC Four-leg Inverter Implementing Novel CMV Elimination for Advanced Motor Drive Applications

Common mode voltage (CMV) has been known to cause EMI in a variety of power electronic inverter applications including motor drive systems where adverse effects include damaging EDM bearing currents. Wide-bandgap (WBG) inverters are being widely implemented due to their higher switching frequencies, efficiencies and power densities compared to traditional Si-based power electronics. However, a significant challenge of utilizing WBG devices in motor drive applications is the increased EMI and EDM bearing currents. This paper presents the development of a SiC four-leg inverter for advanced motor drives employing a novel CMV elimination approach to minimize conducted emissions, prevent damaging EDM bearing currents and enable extended motor lifetimes. The simulation environment and experimental testbed are presented using a Typhoon HIL as the system-level controller including verification simulation results in the Typhoon environment for different deadtimes and filtering. Experimental validation results are presented for the three-phase four-leg inverter using four SiC 1200V, 40A half bridge modules both with the fourth leg connected to the neutral of a 230/460V 5hp motor as well as with the fourth leg only connected to the small inverter output differential mode filter eliminating the need for access to the motor neutral.