A novel common-mode sinusoidal inverter output filter with variable inductor

A long cable between a PWM inverter and a motor results in overvoltage at the motor terminals. A PWM voltage source inverter (VSI) generates common-mode voltage (CMV), which leads to shaft voltage and bearing current. A conventional inverter output filter can eliminate overvoltage when using a longer cable, but cannot achieve better filter effects under all kinds of conditions for its component values which are fixed and have no significant effect on CMV. A novel common-mode sinusoidal inverter output filter with variable inductor is proposed in this paper, which can automatically adjust cutoff frequency of the filter and achieve optimizing sinusoidal waveforms when operation conditions are varying. Simulation and experimental results identify the efficiency of the proposed filter.