Optimization of EMI filter located at the PWM inverter output to reduce parasitic high-frequency currents in AC motor windings

Abstract

Parasitic high-frequency currents in inverter-fed electrical machines are mainly caused by the common-mode voltage with high frequency (HF) and high dv/dt. This will cause severe electromagnetic interference (EMI) problems. Several techniques can be used to reduce these problems. A classical technique is insertion of a passive EMI filter in the system. The design of this filter is usually a "mismatch" type by considering internal impedance of disturbance source and load, equal to 50?; this does not correspond to real impedances of a considered system. The EMI reduction would be less effective. This paper proposes therefore an approach to optimize a low-pass EMI filter adapted to the considered system by using two-port network approach, which is based on real parasitic impedances of the system. This EMI filter optimization is principally dedicated to diminish common mode (CM) high-frequency currents in AC motor windings due to their dominant effects. The efficiency of the proposed optimization approach is deduced by comparing the minimized CM current spectra to an applied normative level such as DO-160D (standard used in aeronautics). ICIC International © 2011 ISSN 1881-803X.