An active circuit for cancellation of common-mode voltage generated by a PWM inverter

TLDR

This paper proposes an active common‑noise canceler (ACC) that eliminates the common‑mode voltage generated by a PWM inverter. The ACC employs an emitter‑follower with complementary transistors and a common‑mode transformer, and the design and construction are detailed. Prototype experiments on a 3.7 kW induction‑motor drive demonstrate that the ACC significantly reduces ground current and conducted EMI, prevents electric shock on a nongrounded frame, and suppresses motor‑shaft voltage.

Abstract

This paper proposes an active common-noise canceler (ACC) that is capable of eliminating the common-mode voltage produced by a pulsewidth modulation (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. Experiments using a prototype ACC, whose design and construction are discussed in this paper, verify its viability and effectiveness in eliminating common-mode voltage in a 3.7 kW induction motor drive using an insulated gate bipolar transistor (IGBT) inverter. Some experimental results show that 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.