Common-mode current inductively coupled emission of AC PWM drives

The most common solution for modern adjustable speed drives is the use of induction motors fed by voltage-source inverters. The inverters using fast switching insulated gate bipolar transistors (IGBTs) generate pulse-width modulated (PWM) voltage pulses. The high carrier frequency along with fast rise and fall time of the PWM switching results in nontrivial common-mode or ground currents noise. The current component can cause electromagnetic interference (EMI) noise to neighbour equipments and installations by either radiation from the motor cable or by cross-talk (inductive and capacitive coupling) with other conductors. This paper discusses the inductively coupled EMI noise from an ac drive system where there susceptible devices and a common ground plant are presented. The model describing the sophisticated EMI phenomenon is proposed and measurement results are presented.