Abstract
The typical motor has poor heat dissipation conditions that are limited by the installation space and working environment, and the high operation temperature increase has been a bottleneck to improve the power density and torque density. The inner rotor motor is considered to be the research object, and an oil-cooling structure for end winding and stator core is proposed. The heat inside the motor is mainly carried away through the lubricating oil in the form of heat conduction and convection heat transfer. The 3d motor model was built using the ANSYS software. The temperature field of the motor was simulated to analyze the temperature distribution inside the motor under rated and peak working conditions. The low-speed high-torque test and one-hour temperature-rise test of the motor prototype were performed on a bench built in the laboratory. The comparison between the test results with water-cooled motor shows that the temperature-rise rate of oil-cooled motor with the same electromagnetic structure is slower than that of water-jacketed cooled motor, and the temperature difference between the front and back of the motor decreases by 18 °C in half an hour. The oil-cooled method has a good cooling effect on the stator core and works for longer time under rated conditions.
Highlights
A hub motor must have high-torque density which can effectively reduce the vehicle under sprung mass
It is necessary to explore the electromagnetic structure of the new hub motor to increase the effective air gap area of the motor
Winding and rotor temperature change under peak condition trend the same drops with oil cooling, but because the winding temperature rises to 160 °C, so the motor cannot measurement with the rated conditions, stator and permanent magnet temperature obviously drops work for a long time under peak conditions
Summary
A hub motor must have high-torque density which can effectively reduce the vehicle under sprung mass. Motor losses are mainly concentrated in the windings and core, so it is necessary to design the cooling structure to make the oil as close as possible to the heat source to improve the cooling effect [14–20]. Heat inside the motor is mainly carried away by lubricating oil in the form of conduction only effectively cool theand end through cool the silicon steel sheet of themethod motor, and convection, the winding, oil is cooledbut by water heat exchange. This oil-cooling canwhich can greatly reduce theeffectively motor internal temperature rise the motor.
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