Research On Rotor Loss And Temperature Rise Characteristics Of Air Bearing High Speed Motor

The high-speed motors have the characteristics of small volume,high power density,large range of speed change and high reliability.Due to these advantages,high-speed motors have good prospects in the fields of aerospace,precision manufacturing and so on.However,because of the high loss in motor and the temperature limits,which becomes a limitation of its use range.The heat dissipation condition on the rotor side is poor,and the permanent magnet is prone to irreversible demagnetization at high temperatures,which affects the normal operation of the high speed motor.The rotor losses of high speed motors are mainly derived from rotor eddy current losses,wind and friction losses,and mechanical losses of bearings.In this paper,the air bearing high speed motor is taken as the research object,and the fluid field model of the air bearing high speed motor is established.The wind field model is used to calculate the wind and rotor loss of the stator and rotor air gap of the high speed motor and the wind and friction loss in the bearing,and the motor is analyzed.The influence of structure and flow field boundary conditions on wind turbine wear of high speed motor was verified by the speed reduction experiment.The rotor eddy current loss model was established to analyze the sheath form of the rotor and the influence of material on rotor loss.The theory establishes the temperature field model of the motor,analyzes the influence of fluid flow state on the heat dissipation coefficient in the air gap,and the difference of the temperature field of the motor under different sheath materials.First,the governing equations for fluids in high speed motors are analyzed.Then according to the characteristics of the air bearing high-speed motor flow field,the fluid field flow state is analyzed,and according to the different flow field action mechanism,the wind-induced friction loss in the stator air gap is divided into two parts: tangential direction and axial direction.The calculation of fluid friction is calculated by computational fluid dynamics method,and the results are compared with the existing empirical formulas of wind and friction loss.The results are consistent.Secondly,the influence of rotor rotation speed,outer diameter,air gap length and air gap boundary condition on wind and friction loss is obtained.Then,according to the flow field model,the pressure velocity distribution under different eccentricities in the air bearing is calculated,and the influencing factors of the wind and friction loss in the radial bearing and the thrust bearing are studied.Then,the wind and friction loss in the motor is separated by the speed reduction experiment,and compared with the calculated value,the accuracy of the error verification calculation model between the two is analyzed.Then,the rotor eddy current loss in the high speed permanent magnet motor was studied.An analytical calculation model of rotor eddy current loss is established,and the influencing factors of rotor side harmonics are analyzed.The effects of carrier ratio,rotor segmentation,sheath material structure and air gap length on rotor eddy current loss are also studied.Finally,based on the analysis results of the fluid field and the calculation of the loss,the temperature field in the high speed motor is studied.The calculation of the heat dissipation coefficient of each part in the motor is analyzed,and the heat dissipation coefficient of the rotor surface in the stator air gap is studied and analyzed.The model of coupling the fluid field and temperature field of the motor is established,and the influence of the rotor sheath material on the temperature field of the motor is studied.