Research on a novel inverter output passive filter for reducing dv/dt at motor terminals in a PWM drive system

A novel inverter output passive filter, which can not only reduce differential-mode dv/dt but also suppress common-mode voltage, is proposed. The filter consists of a LC low-pass filter and a common-mode transformer in series. Its main characteristics are the integration of two kinds of filter operations and simple in structure and design. Analysis, simulation and experimental methods are used respectively to indicate that common-mode voltage are suppressed largely under the condition of satisfying the demand of differential-mode dv/dt filtering which can make differential-mode voltage sinusoidal. All these can contribute to prolong the electric life of the motor. Common-mode equivalent circuit of the filter are also illustrated and analyzed in detail. Some design considerations are also given in the paper. Simulation and experimental results are presented to verify its viability and effectiveness in eliminating common-mode voltage and differential-mode dv/dt.