An Experimental Investigation of the Tradeoff between Switching Losses and EMI Generation With Hard-Switched All-Si, Si-SiC, and All-SiC Device Combinations

TLDR

Silicon carbide (SiC) switching devices provide markedly lower losses than silicon IGBTs, driving interest in replacing Si devices in low‑voltage drives, but their higher switching speeds raise EMI and reliability concerns. The study experimentally quantifies the trade‑off between switching losses and high‑frequency EMI spectral amplitude for all‑Si, Si‑SiC, and all‑SiC device combinations. The results show that the all‑SiC combination reduces switching losses by 70 % relative to all‑Si at comparable dv/dt, yet generates higher EMI, while the Si‑SiC trade‑off can be improved by applying a modified IGBT gate‑voltage profile.

Abstract

Silicon carbide (SiC) switching power devices (MOSFETs, JFETs) of 1200 V rating are now commercially available, and in conjunction with SiC diodes, they offer substantially reduced switching losses relative to silicon (Si) insulated gate bipolar transistors (IGBTs) paired with fast-recovery diodes. Low-voltage industrial variable-speed drives are a key application for 1200 V devices, and there is great interest in the replacement of the Si IGBTs and diodes that presently dominate in this application with SiC-based devices. However, much of the performance benefit of SiC-based devices is due to their increased switching speeds ( di/dt, dv/ dt), which raises the issues of increased electromagnetic interference (EMI) generation and detrimental effects on the reliability of inverter-fed electrical machines. In this paper, the tradeoff between switching losses and the high-frequency spectral amplitude of the device switching waveforms is quantified experimentally for all-Si, Si-SiC, and all-SiC device combinations. While exploiting the full switching-speed capability of SiC-based devices results in significantly increased EMI generation, the all-SiC combination provides a 70% reduction in switching losses relative to all-Si when operated at comparable dv/dt. It is also shown that the loss-EMI tradeoff obtained with the Si-SiC device combination can be significantly improved by driving the IGBT with a modified gate voltage profile.