Cooling design and thermal analysis for dual-stator 6-slot 4-pole flux-switching permanent magnet machine

Abstract

This research report focusses on the thermal management of the electrical machine, which is another important aspect of the machine design. The machine components are often influenced by the variation of temperature, especially for permanent magnet machines. Researchers and engineers have spent many efforts in predicting the temperature distribution and variation in the machine as well as controlling the temperature rise.

The first part of this report recapitulates the commonly used thermal analysis methods, including lumped-parameter thermal network (LPTN), finite element analysis (FEA) and computational fluid dynamics (CFD). The most challenging part for LPTN is the modeling of the machine. Thermal resistance equations for different geometry and different nature of heat transfer (conduction, convection or contact) are given. Example of LTPN is given to illustrate the usage of this method. FEA and CFD tools are more widely used today because of the development in computing capability. Commonly used FEA and CFD tools are introduced, advantages of these numerical tools over the LPTN are presented.

Cooling technologies for electric machines are presented in the second part of this report. Depending on the power rating and the size of the machine, simple cooling such as air cooling as well as advanced high-performance cooling like direct winding cooling are reviewed. The passive cooling has a more reliable structure because of its simplicity, whereas the advanced active cooling has more component. There is a balance between the simplicity, efficiency and cooling requirement. New cooling technologies with simple structure, working principle and high performance are desirable.

After the literature review for thermal analysis method and cooling technology, a case study is conducted for a dual-stator 6-slot 4-pole flux-switching permanent (FSPM) machine. A water jacket integrated housing is used to cool the machine. Since most of the heat source of FSPM machine is on the stator side, therefore, a water jacket could do a good job in removing the heat. Thermal analysis is done based on the cooling design mentioned previously. LPTN and FEA are done and compared. Both steady state and transient temperature distribution are predicted by FEA. The flow characteristic of the coolant in the water jacket is also presented. A prototype machine has been built, the manufacturing design is presented at the end.