High frequency modelling of electric machines using finite element analysis derived data

The use of wide band gap semiconductor switching devices in electric machine drives leads to a significant increase in power density and efficiency compared to conventional silicon-based solutions. However, this technology also presents challenges for the insulation design of electric machines since partial discharges (PDs) may occur due to high peak voltage stress as a result of fast and high frequency switching. To evaluate the risk of PD, it is necessary to understand the voltage distribution within the windings and associated insulation of an electric machine during converter operation. To this end a suitable high frequency model of the machine windings capable of predicting the internal voltage distribution is required. This paper proposes a method of constructing such a model based on finite element analysis (FEA) derived data. The FEA data used to parameterise the model in this work incorporates frequency dependant properties and homogenisation techniques to produce data which captures the high frequency behaviour of the machine. The developed model is compared with measurements in both frequency and time domains, demonstrating the utility and accuracy of the model.