Thermal Modeling and Driving-cycle Critical Temperatures Estimation of Electrically Excited Synchronous Machine for Automotive Traction

Electrically Excited Synchronous Machines (EESM) has garnered attention due to their outstanding performance characteristics but it presents significant thermal challenges. The rotor is embedded with active conductors resulting in a high loss density and large amount of heat that discourage the adoption of this machine in various applications. This paper investigates into the feasibility of utilizing a 60 kW EESM for a commercial vehicle application, with a specific focus on understanding its thermal behavior. Steady-state 3D Conjugate Heat Transfer (CHT) analysis is conducted to obtain the temperature response of various machine components across the torque-speed map. Based on this analysis, thermal resistances are estimated to construct a simplified Lumped Parameter Thermal Network (LPTN) and predict maximum temperatures along the Worldwide harmonized Light-duty vehicles Test Cycles (WLTC). Simulations in MATLAB Simulink show that the temperatures remain below the limits defined by the winding insulation class throughout the entire driving cycle. This finding assures the reliability and safe operation of the EESM for the considered application.