Loss Research And Thermal Analysis Of High Speed Permanent Magnet Synchronous Motor

The characteristics of the power loss and thermal property of the high speed motor differ greatly from common motor, because the speed of rotor and the frequency of the electromagnetic field in the high speed motor are well above the average values in the common motor. In order to ensure the reliability and optimize the design of motor, the distributions of loss and the change in temperature should be calculated accurately. This dissertation researches on the characteristics of the loss and thermal property of high speed permanent magnet synchronous motor. The motivation is to improve the calculation precision of loss and temperature rise and explore the optimal design method from the viewpoint of thermal property.Firstly, based on the calculation of the electromagnetic field in the high speed permanent magnet motor, the loss and its change regularity are analyzed. The analysis of current loss in windings considered the influence of harmonics induced by permanent magnet synchronous motor. The analysis of core loss in the stator is according to the core loss separation theory. The characteristics of the loss in slotted and slot-less permanent magnet synchronous motor are compared.Secondly, on the basis of the calculation of the flow field of the air gap in the high speed motor, the friction loss is analyzed. According to the theory of heat transfer, considering similar rules, the heat transfer coefficient of the surface of motor is calculated. The fluid-thermal interaction model of the high speed permanent magnet synchronous motor is established. And the dynamic temperature change in the motor is presented. Then, to considering the flow state of air and the temperature rise in real time, direct fluid-thermal coupled model is established, and the calculated result of two models is compared. The distinctive model considers the influence of the slot opening in the temperature distribution. Besides, the temperature rise of the motor is tested, which convinced that the calculation method of temperature field in the thesis is correct.Finally, employing the calculation method of temperature field, the influence of convection heat transfer in the temperature profile in the motor is analyzed, including the different thermal convection of the surface of air gap with the slot opening or not and the different heat transfer coefficient for various wind speed. After discuss the influence of the slot structure in thermal property, the changes of temperature field induced by different proportion of power load and magnetic load in slot motor and slot-less motor are researched. At last, the optimal design method of high speed motor from the viewpoint of thermal property is obtained.