New Passive Filter Design Method for Overvoltage Suppression and Bearing Currents Mitigation in a Long Cable Based PWM Inverter-Fed Motor Drive System

High-frequency pulse width modulation (PWM) in inverter-fed induction motor drive systems is widely used in industrial applications because of their flexible speed control and energy savings. However, high dv/dt PWM pulses induce overvoltage spikes on the motor via long cable. Such phenomenon would cause serious deterioration of the motor and cable. A passive overvoltage suppression technique of low-loss "RL-plus-C" filter was proposed recently. It has not only some merits of simple structure, low cost, and good robustness, but also a significant merit of low power dissipation. In order to further mitigate the bearing currents, this paper proposes two new power filters and their design method. The theoretical analysis and the design method are introduced in detail. Experimental results are in good agreement with the theoretical analysis.