Improved Thermal Modeling and Experimental Validation of Oil-Flooded High-Performance Machines With Slot-Channel Cooling

Thermal management is often considered a bottleneck in the pursuit of the next-generation electrical machines for electrified transportation with a step change in power density. Slot-channel cooling is considered to be an effective cooling technique, either as an independent method or as a secondary heat transfer path, which compliments traditional cooling systems. The slot-channel specific geometry and position effects on the thermal benefits are not thoroughly investigated in the literature, while previous work focuses on passing fluid through the unused space left in between coils forming concentrated windings. In this article, slot-channel cooling is implemented within an oil-flooded cooling system for a high power density motor that is used as a pump. A flexible and detailed lumped parameter thermal network (LPTN) is proposed for the cooling system, with the LPTN used to optimize the slot-channel dimensions and location for obtaining maximum thermal benefits. Finally, a surface-mount permanent magnet (SPM) machine with the optimized slot channel geometry is built and tested to validate the thermal model, experimentally achieving an armature continuous current density in excess of 30 A/mm ² .