Multiphysics Analysis and Optimization of Air-Cooled High-Speed Concentrated Winding PMSMs With Auxiliary Teeth

Abstract

Effectively cooling the windings is one of the most important issues for the design and optimization of permanent magnet synchronous machines (PMSMs). Using auxiliary teeth to improve the thermal performance of the machine shows attractive features due to its simplicity. This article thoroughly discusses the impact that the auxiliary teeth have on the magnetic flux distribution, the electromagnetic losses, and the winding temperature. A script capable of predicting the slot fill factor for any slot profile has been developed, allowing its influence on both the equivalent slot conductivity and copper loss density to be considered, which is crucial for electro-thermal analysis. Moreover, a multiphysics framework incorporating a reduced-order thermal model is proposed to optimize a 4-pole/6-slot high-speed PMSM. Back electromotive force and thermal tests with dc excitation are carried out to validate the accuracy of the electromagnetic analysis and the effectiveness of thermal modeling methods, achieving consistent results between experimental and finite element analysis results. The max winding temperature is successfully reduced by 5.69 °C compared with the adoption of an optimized auxiliary tooth since the stator outer surface is air-cooled. The thermal benefits of auxiliary teeth can only be fully realized if adequate cooling capacity is available on the outer surface of the case. The validated thermal modeling method considering the impact of slot fill factor and rotating speed can also be used to estimate the winding temperature in the design stage.