Comparison and suppression of conducted EMI in SiC JFET and Si IGBT based motor drives

This paper compares and suppresses the conducted Electromagnetic Interference (EMI) in Silicon Carbide (SiC) JFET and IGBT based motor drive systems. Two inverter prototypes - with SiC JFETs and Si IGBTs as the transistors are built using the same circuit layout and investigated accordingly. The comparisons start from the transient level of the inverter tested under clamped inductive switching conditions by using of a single inverter leg to the system level conditions of all three phases of each of the inverter drives are functioning. The conducted EMI comparisons include with no fiCM filterslter and with conventional CM filters. To identify the exhibited different filtering performance with the identical filters, two inverters are tested in the CM mode. This allows for the identification and analysis of their maximized CM and DM wave shape differences. The comparisons show that the high frequency noise level of SiC JFET drive under filtered condition is much higher than that of the IGBT´s. Therefore, two methods of inserting ferrite beads at different current paths are proposed to mitigate the increased EMI. Respectively, the middle and high frequency noise of SiC JFET drive system are effectively suppressed to comply with the standard of IEC61800-3: C2.