Review on Thermal Behavior and Cooling Aspects of Axial Flux Permanent Magnet Motors–A Mechanical Approach

Abstract

With the increasing demand for high-energy density motors for applications such as electric vehicles and aircraft propulsion, axial flux permanent magnet motors are promising. However, utmost care should be taken when designing an axial flux permanent magnet motor with a higher torque density because of thermal effects. To enhance the reliability and overall performance of a motor, efficient thermal management is important, because the torque density is restricted by maximum temperature. Therefore, this study comprehensively reviews different techniques used for the thermal modeling of motors. Computational fluid dynamics, the lumped parameter method, and finite element analysis were used to calculate the total heat transfer inside the motor. Various heat enhancement techniques for an axial flux permanent magnet motor have been presented, including core cooling (water jacket cooling, air cooling, and oil cooling) and winding cooling (direct slot cooling, end winding cooling, and fins). Finally, two case studies of an 8kW AFPM motor and a 65kW AFPM motor with a cooling arrangement are discussed.

Thermal Analysis of Stator Iron-Core-Less PMBLDC Motors Considering Both Winding Eddy and Circulating Current Losses

“…Whenever the winding temperature exceeds the maximum values allowed by the insulation class, the insulation life time is heavily reduced by the thermal aging degradation effect [14]. The Joule loss is usually calculated in proportion to the square of the current, which is also known as the dc cooper loss [14]- [18]. In [19]- [20], the thermal characteristics of a high-speed PM machine with slotted and slotless stators were evaluated and compared.…”