A 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 are widely used in industrial applications because of their flexible speed control and energy efficiency. However, high-frequency pulses induce overvoltage spikes to the motor via long cable. Such phenomenon would cause serious deterioration of the motor and cable. A passive overvoltage suppression techniques of low-loss “RL-plus-C” filter has been 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. Based on the design method of “RL-plus-C” filter, this paper presents a new passive filter design method which can both eliminate voltage surges and greatly reduce inverter-induced bearing currents. The theoretical analysis and the design method are introduced in detail. Simulation results are good agreement with the theoretical analysis.