Conducted EMI analysis of a three-phase inverter-motor system in a variable frequency air conditioner

In order to evaluate and improve the electromagnetic compatibility (EMC) of a variable frequency air conditioner, a time-domain methodology is advanced to analyze the conducted electromagnetic interference (EMI) caused by the three phase inverter-motor system in an actual air conditioner. The parasitic parameters of the EMI propagation path in the air conditioner are extracted using impedance measurement and finite element method (FEM). The EMI noise sources of the inverter are modeled by three switching voltages according to its operating principle. Simulation based on these models is performed. The EMI spectrum matches with the measurement one, which validates the high frequency (HF) circuit models, and indicates that the methodology is effective to evaluate the conducted EMI for a three phase inverter.