AN ACTIVE CIRCUIT FOR CANCELLATION OF COMMON-MODE VOLTAGE GENERATED BY A PWM INVERTER

This paper proposes an active common-noise canceler (ACC) that is capa ble of eliminating the common-mode voltage produced by a pulsewidth mo dulation (PWM) inverter, An emitter follower using complementary trans istors and a common-mode transformer are incorporated into the ACC, th e design method of which is also presented in detail. Experiments usin g a prototype ACC, whose design and construction are discussed in this paper, verify its viability and effectiveness in eliminating common-m ode voltage in a 3.7-kW induction motor drive using an insulated gate bipolar transistor (IGBT) inverter. Some experimental results show tha t the ACC makes significant contributions to reducing a ground current and a conducted electromagnetic interference (EMI), In addition, the ACC can prevent an electric shock on a nongrounded motor frame and can suppress motor shaft voltage.