Investigation of Motor Winding Overvoltages in Integrated WBG-Based Motor Drive Systems

Cable-connected motor winding insulation is prone to failures owing to reflected wave (RFW) overvoltages (OV). RFW is caused by the impedance mismatch between source and load and impacted by the impedance interactions of the motor drive system and pulse width and risetime of the excitation source. According to the literature, the OV across the motor winding is less detrimental in an integrated motor drive due to the absence of cable. However, in this paper, two scenarios are shown which can cause detrimental voltage stress across the winding in an integrated wide band gap (WBG)-based drive system. First, WBG-based motor drive generates short risetime and short pulse width that excites the higher frequency resonance network of the integrated motor winding. So, it brings higher OV amplitude across the motor winding. Second, voltage stress across motor winding is shown to worsen when the antiresonance of the winding (least impedance) coincides with OV resonance frequency across it, termed as antiresonance phenomenon (ARP). Due to the absence of cable, the ARP is bound to happen in an integrated drive system. Experimental results are given to validate the claims.