Over Voltage due to Cable Reflections at SiC Converters – Basic Effects and Countermeasures

Abstract:
The undesirable effects of cable reflections in connection with voltage-source converters are known since long. In typical applications with inductive loads they cause overvoltage at the load, in applications with electric machines they increase the risk of bearing damage by spark erosion. In addition, challenges in the area of electromagnetic compatibility are caused. The length of the cable and the steepness of the converter output voltage determine the severity of the effect. Wide band-gap devices cause voltage transients of several 10 kV/mus - giving relevant overvoltage already at a cable length of few meters. Efficient countermeasures with low impact on converter efficiency help to mitigate these effects and are discussed in this paper.