Active filter for an induction motor drive with a long cable

Abstract

Inverter-fed induction motor can be severely stressed under a long connected cable. In particular, fast-switching Pulse Width Modulation (PWM) pulses will cause overvoltage at the motor terminals and the motor windings. The doubling of the supply voltage will further stress the motor insulation, which will eventually cause motor malfunction. This paper studies the working principle of an active filter in three-phase circuit to minimize the voltage surge and adjust the rise time of PWM pulses. An auxiliary power supply circuit is also designed to self-power up the active filter. The supply voltage of the new designed auxiliary power supply circuit can be obtained from the capacitor CDC in the active filter circuit. In the designed circuit, two buck circuits are built to step-down the high voltage stored in the capacitor. The output voltage of 5V and 15V of the designed power supply circuit will be fed back to the ICs and MOSFETs in use in the active filter. The validity of the proposed active filter circuit and the auxiliary power supply circuit is supported by both the simulation and experimental results, in which is found to be in good agreement.