Research On Oil Cooling In Groove System Of High Torque Density Concentrated Permanent Magnet Motor

The electric motors are becoming more and more severe on power density and torque density for electric vehicles.The heat dissipation of motor has become an important factor to limit the motor performance.In this paper,a new type of oil cooling in groove is proposed based on concentrated winding permanent magnet motor for electric vehicles,which lead to remarkable cooling effect,especially for high torque density.At the same time,optimize the cooling effect of the motor in high speed under overload condition is guaranteed.This paper studies on the structure of oil cooling in groove suitable for electric vehicles with concentrated winding permanent magnet motor and makes deep researches on motor losses,electromagnetic-thermal coupling on structure design and experience of motor heat transfer.The main contents are as follows:Firstly,this paper summarizes the calculation methods of various kinds of motor losses,and the key problems that should be paid attention to when studying various kinds of losses are pointed out.The calculation of the iron loss coefficient and the distribution of iron loss are emphasized,which lays the foundation for accurate study of the motor temperature field.On this basis,to do a comparative analysis between the structure of oil cooling in groove and casing water-cooling and structure of oil mmersion,and the focus is on the analysis of cooling characteristics of the structure of oil cooling in groove to provide guidance for the design of cooling structure of the motor.Secondly,in this paper,study on key problems of structure design of oil cooling in groove,and mainly including the influence of allocation of slot space and air gap length on the electrical performance and cooling performance from the spatial distribution of given groove theoretical conclusion.The installation of cooling pipe in the motor slot affects the full rate of the motor slot.Further more,the electromagnetic performance of the motor is analyzed,and the cooling effect of the motor is improved under the premise of ensuring the electromagnetic performance of the motor.According to the design result,the heat dissipation effect of the motor under different working conditions is verified by the finite element method.Furthermore,the law of heat conduction of the key components in the motor and the change of the heat conduction mode of the motor under different working conditions are of great significance to the design of the motor cooling structure.The thermal network model of different cooling modes of motor is established.The heat flow in the motor under different cooling modes and different operating conditions is studied.The selection rules of different cooling modes are given.At the same time,combined with the actual motor prototype,in the thermal network model,the influence of the motor slot insulation and the air cavity on the motor cooling is studied.Finally,to optimize oil cooling in groove system with the thermal network model and three-dimensional finite element,mainly from enhencing heat dissipation in high speed condition and optimization of cooling parameters.The purpose is to achieve the balance and optimization between electromagnetic performance and the cooling effect of the motor.