Z-matched active common-mode canceller for the suppression of common-mode current in an inverter system

In a vehicle, radiational noise generated by the common-mode current in an inverter system is the cause of electromagnetic problems of in-vehicle radio antennas. This paper proposes a new method ”Z-matched ACC” for suppressing the common-mode current at AM band. With this method, the freewheel current, which reduces the common-mode current suppression effect at AM band in conventional voltage-cancellation ACC, does not flow by setting the phase of the Z-matched circuit equal to that of the motor common line. Therefore, the Z-matched ACC can suppress the common-mode current at AM band. The suppression effect of the Z-matched ACC is superior to the conventional ACC from 100 kHz to 10MHz. In addition, the Z-matched ACC can reduce the size of the common-mode transformer over that for the conventional ACC by reducing the ET product applied to the common-mode transformer.