Quantitative Analysis of Filter Parameters in an Electric Motor Drive

Wide band-gap (WBG) power devices are increasingly being utilized in variable frequency drives (VFDs) to enhance efficiency and decrease overall size. These devices however, degrade motor terminals from over-voltage when paired with long cables and can cause bearing currents from quickly changing common mode voltages. Common mode and dv/dt filters are used to mitigate these effects but are often excessive to fit a wide range of systems. In this paper two combined dv/dt and common mode filters are quantitatively analysed. The effects of system constraints on the resulting filter are investigated by first modeling the system accurately, validating the model experimentally and simulating the performance of a range of filter parameters. The results show that access to the DC link midpoint can improve the common mode filter performance by up to 51.9%.