Improved hotspot monitoring method for thermal management system of automotive traction motor

Hotspots in traction motors of electric vehicles are normally considered to locate in end windings due to the loose packaging and no access to iron cores for heat dissipation. To ensure safety, end winding temperatures are typically monitored by thermocouples in thermal management systems for real-time cooling control. However, the authors’ study finds that slot winding temperatures will exceed end winding temperatures under high-speed operations due to the much higher additional loss caused by the alternating flux. Hence, the thermocouple would underestimate the actual peak temperature in electric machines, causing insufficient cooling and potential damage to insulations. For cost savings, additional thermocouples monitoring slot winding temperatures are usually not equipped in the automotive industry. To calibrate the peak temperature of windings, this study proposes an innovative approach based on the thermo-magnetic model of the traction motor, which provides the estimated slot winding temperatures only using the end winding sensors. As a result, the proposed method can provide much accurate peak temperatures for the thermal management system. Experimental tests validate the performance of the proposed method in improving the accuracy of hotspot monitoring.