Permanent magnet synchronous motors are highly preferred in electric vehicles, but the thermal management of PMSMs are important for their reliability and insulation lifetime. For this purpose, this thesis aims to develop the simplest temperature estimation and aging calculation to implement into the Thermal Management System of an electric vehicle with the best trade-off. Starting from a seven-node reference thermal model, several reduced-order models are developed by merging or taking equivalent thermal nodes and heat-transfer paths. The temperature profiles of the winding are compared with the reference model to evaluate the effects at different detail levels. In addition, an Arrhenius–Miner thermal aging model is implemented, where the estimated winding temperature is used to calculate the damage and motor state of health.