An Active Cancellation Circuit for Reducing Electrical Noise from Three-Phase AC Motor Drivers

A novel active cancellation circuit for reducing common-mode (CM) noise in vehicular three-phase ac motor drives is described. The cancellation circuit features a feed-forward voltage-detecting-voltage-compensating structure. Unlike other voltage-compensating circuitry employing CM transformers on the thick phase wires, the proposed circuit is compactly integrated on the inverter printed circuit board. A prototype low-voltage space-vector-pulse-width-modulation (SVPWM) inverter employing this active cancellation technique was built and tested. This cost-effective and light-weight circuit significantly reduced the CM noise at the fundamental switching frequency and harmonics up to 2 MHz.