MEASUREMENT AND REDUCTION OF EMI RADIATED BY A PWM INVERTER-FED AC MOTOR DRIVE SYSTEM

This paper presents theoretical and experimental relationships between radiated electromagnetic noises and common-mode and normal-mode curre nts, paying attention to an induction motor drive system fed by a volt age-source pulsewidth modulation (PWM) inverter. A method of reducing both currents is proposed, based on an equivalent model, taking into a ccount parasitic stray capacitors inside an induction motor. Electroma gnetic interference (EMI) radiated by a 3.7-kW induction motor drive s ystem is actually measured, complying with the VDE 0871 Class A [3 m]. Experimental results verify that the combination of the already propo sed common-mode transformer (CMT) and the normal-mode filters (NMF's) being proposed in this paper is a practically viable and effective way to reduce EMI resulting from both common-mode and normal-mode current s.