CARRIER NOISE REMOVING FILTER FOR PWM INVERTER

PROBLEM TO BE SOLVED: To restrain the equivalent capacity of an AC capacitor when viewed from system side by connecting a bypass filter between a reactor, a PWM inverter and a neutral position of three phases, and switching the AC switch of the bypass filter with the outputted voltage signal of the PWM inverter. SOLUTION: A bypass filter with a serial circuit consisting of an AC capacitor 15 and an AC switch 16 is connected between a reactor 13, a three-phase PWM inverter 14, and a neutral position of three phases, or between the reactor 13 and the connecting point of the three-phase PWM inverter. The AC switch 16 of the bypass filter is switched with the outputted voltage signal of the three-phase PWM inverter 14. It is thus possible to absorb the carrier noise of the three-phase PWM inverter 14 by equivalently-reducing the capacity of the AC capacitor 15 when viewed from the system side, and restrain the advanced capacity of the AC capacitor 15 and inflow higher harmonic current from increasing.