A very low-loss motor overvoltage suppression filter using energy recovery concept

Overvoltage phenomenon occurs at AC motor terminal fed by pulse width modulation (PWM) inverter drives. To protect the motor against insulation damage, many passive filter networks such as RLC filter and RC filter have been developed. However, they are either physically large and generally energy inefficient or cannot alter the wavefront of the pulses at the motor terminal to improve the inter-coil and inter-turn voltage distributions in the motor. This paper presents a motor protection filter with energy recycling which can protect the motor against insulation damage and works out the drawbacks of most recent filter networks. It has very small power loss comparing with the commonly used filters. The method is based on recycling the energy gained from suppressing the motor terminal voltage back to the whole system. An experimental filter has been built and evaluated on a 1-hp three-phase motor drive system. A comparative study into the performance among the commonly-used RC filter, RLC filter and proposed filter will be provided.