Reduction of Radiated Noise Using Two Inverters for Motor Drive Operating in Opposite Phases

Various cancellation techniques regarding the common-mode voltage of motor drives have been investigated. In this paper, we demonstrate an antiphase Pulse Width Modulation (PWM) operation by two inverters for motors driving operating in opposite phases. An antiphase PWM operation can reduce not only common-mode current but also radiated noise. The reduction effect of the common-mode current is verified experimentally on the basic experimental system up to 3 MHz. Additionally, the reduction effect of the radiated noise is verified experimentally on the actual product system up to 2 MHz. As the frequency becomes higher, the reduction effect of the antiphase PWM operation becomes lower. The reason is considered from the viewpoints both of the common-mode current path and the time waveform of the common-mode current. In the frequencies range from 10 kHz to 150 kHz, the reduction effect of the radiated noise by the antiphase PWM operation is higher than that with inserting the magnetic cores. The methods for suppression of the radiated noise by antiphase PWM operation can provide miniaturization of the inverter equipment. The noise reductions are investigated not regarding EMI applicable standards and limits, but the interference to radio‐frequency spectrum up to 3 MHz in the telecommunication equipment.