Design, Optimization and Modelling of High Power Density Direct-Drive Wheel Motor for Light Hybrid Electric Vehicles

Throughout the last few years, permanent magnet synchronous motors have been proven suitable candidates for hybrid electric vehicles (HEVs). Among them, the outer rotor topology with surface mounted magnets and concentrated windings seems to be very promising and has not been extensively investigated in literature. In this study, an overall optimization and modelling procedure is proposed for the design and operational assessment of high-power density direct-drive in-wheel motors, targeted towards a light HEV application. The analytical model of an HEV’s subsystems is then implemented for a more accurate evaluation of overall powertrain performance. Furthermore, a simple but effective cooling system configuration, which is taking into account the specific problem requirements, is also proposed

Thermal Modeling of Permanent Magnet Synchronous Motors for Electric Vehicle Application

Permanent magnet synchronous motor (PMSM) is a better choice as a traction motor since it has high power density and high torque capability within compact structure. However, accommodating such high power within compact space is a great challenge, as it is responsible for significant rise of heat in PMSM. As a result, there is considerable increase in operating temperature which in turn negatively affects the electromagnetic performance of the motor. Further, if the temperature rise exceeds the permissible limit, it can cause demagnetization of magnets, damage of insulation, bearing faults, etc. which in turn affect the overall lifecycle of the motor. Therefore, thermal issues need to be dealt with carefully during the design phase of PMSM. Hence, the main focus of this thesis is to develop efficient ways for thermal modeling to address thermal issues properly. Firstly, a universal lumped parameter thermal network (LPTN) is proposed which can be used for all types of PMSMs regardless of any winding configuration and any position of magnets in the rotor. Further, a computationally efficient finite element analysis (FEA) thermal model is proposed with a novel hybrid technique utilizing LPTN strategy for addressing the air gap convection in an efficient way. Both proposed LPTN and FEA thermal models are simplified ways to predict motor temperature with a comparatively less calculation process. Finally, the proposed thermal models have been experimentally validated for the newly designed interior and surface mounted PMSM prototypes. Again, a procedure for effective cooling design process of PMSM has been suggested by developing an algorithm for cooling design optimization of the motor. Further, a computational fluid dynamics (CFD) model with a proposed two-way electro-thermal co-analysis strategy has been developed to predict both thermal and electromagnetic performance of PMSM more accurately considering the active cooling system. The developed step algorithm and CFD modeling approach will pave the way for future work on cooling design optimization of the newly designed interior and surface mounted PMSM prototypes