A new inverter output passive filter topology for PWM motor drives

In this paper a new inverter output filter is proposed. The proposed filter is comprised of a conventional resistance, inductance, capacitance (RLC) network cascaded with an LC trap filter and an additive coil on the inductor of the RLC filter. The scheme is very effective in reducing the switching harmonics, suppressing the common-mode voltage and reducing differential-mode d(v)/d(t). This paper illustrates and analyzes the common-mode and differential-mode equivalent circuit of the filter in detail. The voltage transfer functions of the differential-mode circuit and the common-mode equivalent circuit are analyzed. An engineering design method of the filter parameters is presented. The experiments with a conventional filter and the proposed filter are also done. The comparison verifies the proposed filter viability and effectiveness in eliminating in eliminating common-mode voltage and differential-mode d(v)/d(t).