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 capable of eliminating the common-mode voltage produced by a PWM inverter. An emitter follower using complementary transistors and a common-mode transformer are incorporated into the ACC, the design method of which is also presented in detail. A prototype ACC designed and constructed in this paper verifies the viability and effectiveness in a 3.7 kW induction motor drive using an IGBT inverter. Some experimental results show that the ACC makes significant contributions to reducing ground current and conducted EMI. In addition, the ACC can prevent electric shock on a ungrounded motor frame and can suppress motor shaft voltage.