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 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 a ground current and a conducted EMI. In addition, the ACC can prevent an electric shock on a non-grounded motor frame and can suppress a motor shaft voltage.