Passive EMI Filter Performance Improvements with Common Mode Voltage Cancellation Technique for PWM Inverter

The common modulation strategy adopted for motor control in adjustable speed drives (ASDs) is pulse width modulation (PWM). The carrier frequency along with fast rise and fall time of the IGBTs employed results in non trivial common-mode (CM). The high dv/dt and di/dt causes shaft-voltage, which leads to bearing currents. This phenomenon has been well-known as one of the reason for premature bearing failure in PWM drive motors. To reduced EMI emission, this paper presents the experimental works that investigate the conducted emission from pulse width modulated (PWM) inverter feeding an induction motor using CM voltage cancellation technique to develop the ability of conventional passive EMI filter. The typical passive EMI filter also use in this work to compare and prove the effectiveness proposed method. The experimental results of two operation conditions: with load and without load are verified the effectiveness of proposed filters, respectively.