| Interior permanent magnet synchronous motors are widely used in high-end equipment because of their high efficiency,high power density and wide speed regulation range.With the development of miniaturization and light-weight of motor in different application fields,the power density and electromagnetic load of motor increase sharply,saturation is serious,loss and temperature rise are high.This paper focuses on the temperature rise and cooling of the IPMSM,the cooling structure design,fluid and temperature field calculation,magnetic field and loss calculation,multi-mode electromagnetic-thermal coupling calculation method are studied.In order to solve the problems of limited air flow path and too high temperature rise at the axial center of the rotor in a closed motor,a new structure with inclined rotor end deflector is proposed to reduce the temperature rise.On this basis,the ventilation path of the motor is analyzed,and a scheme of circulating convection between rotor holes is proposed to increase the air velocity and reduce the loss of wind resistance.The mathematical and simulation model of a 40 KW IPMSM were established,and the fluid field and temperature field distribution of the motor were analyzed by computational fluid dynamics simulation,it is verified that the proposed cooling structure has significant cooling effect and low wind resistance loss.To solve the problems of time-consuming numerical simulation,complicated calculation process and low efficiency of cooling structure design,a lumped parameter model of motor is established in view of the basic theory of fluid mechanics and heat transfer,the air velocity distribution and temperature field distribution in the motor are solved.In the fluid network model,according to the theory of blade element,the calculation method of the guide vane pressure is proposed,and the mapping relationship between the vane parameters,the rotating speed and the vane pressure is deduced.Based on the numerical fitting method,the spiral correction coefficient is proposed to better consider the effect of rotor rotation on the frictional pressure drop.In the heat network model,the geometric structures of the heat transfer surfaces of each part of the motor are classified and equivalent,and the experimental correlations of convective heat transfer coefficients with high accuracy are given.On the basis of the lumped parameter model,the influence of the structure parameters of the guide plate on the air flow and temperature rise is analyzed.Based on the electromagnetic and temperature characteristics of ferromagnetic materials,the electromagnetic and temperature characteristics of ferromagnetic materials are analyzed,the improved equivalent magnetic network model of the motor is established considering the effect of temperature and parameter change.The current harmonics are calculated according to the parameters of the motor,and the distribution of the flux density is obtained by adding the current harmonics into the calculation of the magnetic network.On this basis,the calculation model of temperature-dependent loss is given,and the influence of temperature and current harmonics on the loss is revealed.The electromagnetic-thermal coupling model is established by combining the established electromagnetic and loss calculation model with the thermal network model,and the variation laws of electromagnetic parameters,loss and temperature rise of the motor are studied.To obtain the performance of the motor in close to the actual operation situation,based on the electromagnetic-thermal coupling model mentioned above,combined with the operating condition of the motor and the corresponding control method,the parameters,loss and temperature distribution of the motor under different operating conditions are studied.The calculation results of the electromagnetic-thermal coupling model and the independent model without the influence of temperature are compared and analyzed,and the variation laws of motor parameters,loss and temperature with speed and torque under different control strategies are revealed,which provides the basis for the electromagnetic design and check of the motor.Finally,according to the 40 k W IPMSM’s electromagnetic and cooling structure,the prototype is made,and the electromagnetic performance and temperature rise of the prototype under various working conditions are simulated and tested,it is verified that the electromagnetic-thermal coupling model established in this paper has high accuracy. |
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