Power loss, system efficiency, and leakage current comparison between Si IGBT VFD and SiC FET VFD with various filtering options

SiC devices have received strong attention as the next generation power device. This paper compares the power loss and efficiency between two options that can be used with SiC based Variable Frequency Drives (VFDs). In the first option, the SiC based VFD is equipped with an output sine wave filter and the carrier frequency is 50 kHz. A dv/dt filter is used for the second option with the carrier frequency reduced to 8 kHz. Both the results are finally compared with a standard Si IGBT based VFD operating at a carrier frequency of 8 kHz with no output filter. The focus of the paper is to present different options to the drives industry in adopting SiC based VFDs which will soon become a standard product in the marketplace. The dv/dt filter is designed to meet the same specification as that of the standard Si IGBT based VFD with no output filter. This was deliberately done to present a fair comparison between a standard Si IGBT based VFD and the next generation SiC based VFD, from performance and loss points of view. A system rated at 460V, 11kW is used for all comparison tests. Results show that the SiC VFD with output sine wave filter has lower efficiency compared to SiC VFD with a dv/dt filter. Influence of the various filtering options on the leakage current in the motor drive system has also been studied and the results are presented in this paper.