Research on Reduction of EMI Produced by a Valiable-Speed Motor Drive System with a PWM invester

点击翻译按钮获取中文摘要

This research aimes to clarify mechanism of generating both radiative and conductive noises and to develop reduction methods of the noises, in variabile-speed AC motor drive system using a voltage-source PWM inverter.First of all, for a three-phase AC motor, we have proposed a high-frequency equivalent consisting of only three capacitors each of which connects between a motor terminal and a motor frame. Experiment using an induction motor drive system (3.7 kW) and simulation using a circuit simulator have demonstrated that the proposed high-frequency equivalent circuit can simulate both common- and normal-mode currents caused by switching operation of the PWM inverter with enough accuracy. Moreove, based on the proposed equivalent circuit, we have developed "common-mode transformer (CMT), " which acts as a resistance only to the common-mode current, and "normal mode filter (NMF), " which can dump the high-frequency oscillating current flowing between two phase of the motor, and design … More methods for these components have been studied in detail. In addition, it has been shown theoretically and experimentally that the CMT and NMF can reduce not only EMI but also serge voltage appearing on a motor terminal at a switching instant of the inveter.On the other hand, we have proposed an "active common noise canceler (ACC)" which can cancel the common-mode voltage using an active element, in contrast to the conventional components. The operation and effect have been confirmed by some experiments, and the design method has been studied in detail. The patent applications for the ACC have been made to Japan and United States through the Japan Society for the Promotion of Science. The patent applications for the ACC have been made to Japan and United States through the Japan Society for the Promotion of Science.Finaly, we believe that the results obtained by this research contribute to advancement of theoretical and systematic research of EMI/EMC occurring in power electronics apparatus. Less