Investigation into the temperature profile of a liquid cooled YASA© AFPM machine

The developments in Axial Flux Permanent Magnet (AFPM) machines enable higher torque and power densities and higher efficiencies, thus making it a suitable candidate for various applications such as electric road transportation or wind energy generation. Due to the fact that liquids have a higher thermal capacity than air, liquid cooling has been used in high power radial flux electrical machines. This typically involves water being passed through a series of channels in the casing, which will be in thermal contact with the stator. Such a cooling configuration presents a number of thermal resistances between the heat source and the heat sink, limiting the heat transferred and hence the performance of the machine. The knowledge developed for radial flux machines, has been transferred to the design of AFPM machines, with the cooling channels embedded in the stator iron or in the stator plate for single rotor machines. Such liquid cooled machines rely on air-cooling for the copper end windings. The scope of this work is to present a temperature profile for a pole piece for a liquid cooled stator in YASA© electric machine. A high-resolution lumped-capacity thermal model is also presented, and compared to the experiment. The paper shows how a high-resolution model can reveal much more valuable information on the thermal aspects of the stator.