Influence of Induction Motor Power Rating on EMI Noise in Grid-Fed Motor Drive Systems

The common-mode (CM) and differential-mode (DM) impedance play a crucial role in determining electromagnetic interference (EMI) noise in grid-fed motor drives. The impedance characteristics of an induction motor (IM) vary significantly with its power rating and physical structure, both which directly influence its parasitic elements. However, the impact of motor size on CM and DM impedance, as well as its effect on EMI noise—particularly in the SUPRA EMC range (2 kHz to 150 kHz) and conducted emissions (150 kHz to 30 MHz) has been rarely explored together. This paper investigates the influence of motor parasitic parameters by analyzing measured CM and DM impedance plots for IMs in the 0.55 kW–500 kW power range. A high frequency motor model is then employed to quantify CM and DM noise and assess the impact of impedance variations on EMI noise propagation for 1.1 kW and 55 kW IM using Q-spice.