Correction of Winding Peak Temperature Detection in High-Frequency Automotive Electric Machines

Abstract

The insulation material applied on the stator windings of automotive electric machines are susceptible to the excessive temperature rise. Typically, several thermocouples are embedded in the end-winding and the active winding in the slot to detect the peak temperatures in real-time to avoid thermal damage and adjust cooling. However, in the slot windings, the uneven distribution of power loss will change with frequency. This phenomenon causes the movement of the hotspot in the slot winding at different operating states, while it is not so obvious in the end-winding. As a result, the peak temperature in the slot winding cannot always be detected exactly by the fixed thermocouples, which has never been realized and valued. In this article, we analyze the movement of the hotspot in both of the slot winding and end-winding. In order to improve the detecting precision, we use an offline theoretical thermal-magnetic model to deduce the relationship between the temperatures at the measured position and real hotspot at various operating states. Then the thermocouple reading can be corrected in real-time according to the deduced relationship. The experimental test validates the performance of the proposed method in elevating the precision of peak temperature detection.