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This paper presents an equivalent circuit for high-frequency leakage currents in pulsewidth modulation (PWM) inverter-fed AC motors, which forms a series resonant circuit. The analysis based on the equivalent circuit leads to such a conclusion that the connection of a conventional common-mode choke or reactor in series between the AC terminals of a PWM inverter and those of an AC motor is not effective to reduce the rms and average values of the leakage current, but effective to reduce the peak value. Furthermore, this paper proposes a common-mode transformer which is different in damping principle from the conventional common-mode choke. It is shown theoretically and experimentally that the common-mode transformer is able to reduce the rms value of the leakage current to 25%, where the core used in the common-mode transformer is smaller than that of the conventional common-mode choke
AC motor drives
Digital Object Identifier: 10.1109/28.536872
Published with permission from the copyright holder. This is the institute's copy, as published in Industry Applications, IEEE Transactions on, Sept.-Oct. 1996, Volume 32, Issue 5, Pages 1105-1114.
Copyright © 1996 IEEE. All rights reserved.