Comparison of Temperature Characteristics of Outer Rotor LSPMMs Under Different Cooling Structures

For low-speed permanent magnet motors (LSPMMs), the winding copper loss accounts for most of the total loss, which resulting in the winding to become the hottest spot of the entire motor. Excessive winding temperature would cause insulation damage or reduce the service life of the motor. Therefore, it is necessary to adopt efficient cooling methods to reduce the winding temperature. In this article, two efficient cooling structures are analyzed: a high thermal conductivity path (HP) placed in the middle of the winding and the end winding potting. On the one hand, the influence of different factors on the temperature characteristics of each cooling structure is analyzed through 3-D finite element analysis (FEA). On the other hand, based on the water-cooled structure and two efficient cooling structures, four cooling schemes are designed and their winding temperature distributions are compared, so as to obtain the effect of different cooling structures on winding temperature and the interaction between different cooling structures. Finally, two prototypes with different cooling structures are fabricated and the electromagnetic and temperature characteristics are tested to verify the theoretical analysis.