Liu, Z., Winter, T., and Schier, M., "Direct Coil Cooling of a High Performance Switched Reluctance Machine (SRM) for EV/HEV Applications," SAE Int. J. Alt. Power. 4(1):162-169, 2015, doi:10.4271/2015-01-1209.
This paper presents the development of a novel direct coil cooling approach which can enable high performance for electric traction motor, and in further significantly reduce motor losses. The proposed approach focuses on bypassing critical thermal resistances in motor by cooling coils directly in stator slots with oil flow. Firstly, the basic configuration and features are shown: sealed stator slots to air gap, pressure reservoirs on both side of the slots and slot channels for oil flow. The key to enhance thermal performance of the motor here is based on introducing fluid guiding structure in the slot channels. Next, heat transfer in the channel with guiding structure is investigated by CFD and compared with bare slot channel without guiding structure. For studying the effectiveness of proposed cooling concept, numerical analysis is conducted to compare it with HEV favored oil impingement cooling. Finally, thermal performance of the proposed cooling approach is verified and compared with water/glycol jacket cooling on a switched reluctance machine prototype for EV application inside a public funded project ODIN.