Advanced Thermal Management of High Torque Density Permanent Magnet Machines

Advanced thermal management is a critical field that can improve the electrical machine performance in terms of the torque and power density, efficiency, reliability, and maintenance. This thesis delves into advanced thermal management for high torque density permanent magnet machines. It explores a novel machine configuration that introduces stator modularity in a surface-mounted permanent machine. The influence of the flux gaps on the machine electromagnetic, fluid dynamics, and heat transfer performances has been investigated in this thesis. In order to accurately predict the influence of different cooling technologies on machine electromagnetic performance, an electromagnetic-thermal coupled model is established based on finite element method, computational fluid dynamics, and lumped parameter thermal network methods. Comparative studies involved the static electromagnetic performance, such as torque and torque ripple, as well as dynamic electromagnetic performance, such as torque speed curve and efficiency map, have been investigated, while considering the electromagnetic-thermal coupling. To further elucidate the impact of flux gaps, the coupled model has been employed to investigate the modular SPM machine and its non-modular counterpart with two different advanced cooling technologies: including semi-flooded oil cooling and ventilation cooling. Additionally, multiphysics models, incorporating magnetic body forces in computational fluid dynamics simulations, have been developed to examine thermomagnetic convection in ferrofluid cooling. The cooling efficiency of ferrofluid cooling methods under different load currents and various coolant properties has been assessed by employing this multiphysics model. Moreover, the impact of flux gaps on the ferrofluid cooling system has also been revealed in this thesis. In summary, this thesis comprehensively investigates the influence of flux gaps on machine electromagnetic, fluid dynamics, and heat transfer fields using finite element, computational fluid dynamics methods and their coupled models.