Effect of Cooling Strategies on Performance of Rotor PM and Stator PM Machines

This paper investigates the effect of various cooling strategies, including forced air, water jacket, and shaft cooling, as well as their combinations, on the output torque and power of rotor PM and stator PM machines. Finite element analysis and computational fluid dynamics are used for analyzing the torque and power capabilities accounting for the thermal limits of PM and winding insulation. It is shown that hybrid water jacket and shaft cooling can significantly extend the operational region of surface-mounted PM machines, while only water jacket cooling is required in switched-flux PM machines to produce a competitive torque.