Impact of mismatch cables impedances on active motor terminal overvoltage mitigation using parallel voltage source inverters

Abstract

Non-treated transient motor terminal overvoltage due high-speed switching sources and long cable length can be twice the original source voltage amplitude. In some cases, this overvoltage can cause premature motor insulation failure. A topology widely applied in industry is subject of this overvoltage: motors driven by voltage source inverter, connected by long feeding cable. There are several passive methods effective in mitigating overvoltage, but most of them are based in lossy and bulky passive component filters. A different approach is proposed by two low loss active methods for overvoltage mitigation with simple topologies. It consists in using voltage source inverters with specific switching strategy in order to attenuate the main cause of overvoltage: the superposition of traveling reflected pulses at the motor terminals. As promising methods for overvoltage mitigation, some specific studies regarding its particularities must be carried on in order to clear understand all its benefits and possible drawbacks. The present paper discusses the vulnerability of these overvoltage mitigation methods to some internal parameter variation. The impact of cables impedance variation due heating –and impedance mismatch– is highlighted, since it is intrinsic to the system and can degrades overvoltage mitigation.