Thermal analysis of fault-tolerant electrical machines for more electric aircraft applications

For safety critical applications, electrical machines need to satisfy several constraints, in order to be considered fault-tolerant. In fact, if specific design choices and appropriate control strategies are adopted, fault-tolerant machines can operate safely even in faulty conditions. However, particular care must be taken for avoiding uncontrolled thermal overload, which can cause severe failures. This study describes the thermal modelling of a three-phase, synchronous machine for aerospace applications, analysing the machine's thermal behaviour under open-circuit fault conditions. A particular winding's layout is chosen with the purpose of satisfying fault-tolerance constraints. The winding temperature is evaluated by using a simplified thermal model, which was experimentally validated. Copper and iron losses, necessary for the thermal simulations, are calculated analytically and through electromagnetic finite element analysis, respectively. Finally, an aerospace study case is presented and the machine's thermal behaviour is analysed during both healthy and open-circuit conditions.