Simulation methods play a fundamental role in the development of electric powertrains to optimize vehicle performance, cost and streamline the control development. In this context, this study focuses on the development of a methodology for the evaluation of a battery electric vehicle (BEV) powertrain, by means of the CAE multi-physics simulation software GT-SUITE. First, the case study and the powertrain components are presented including battery pack, inverter with capacitor DC-Link and PM motor. Their function, the requested input data and the modelling criteria are discussed. Subsequently, an electrical-equivalent thermal model for the inverter is proposed, for the evaluation of the instantaneous junction temperature of the switches.