Research On Temperature Rise Of Three-phase 6/4 Structure Switched Reluctance Motors

Firstly,this paper introduces the research background and significance of temperature rise of switched reluctance motor,as well as the research status at home and abroad.It analyses the advantages and disadvantages of three commonly used methods for calculating temperature rise of switched reluctance motor,namely,simplified formula method,equivalent thermal circuit method and finite element method,and clarifies the research process of temperature rise of switched reluctance motor in this paper.Secondly,the mechanical structure of switched reluctance motor is analyzed.In order to facilitate the establishment of equivalent thermal circuit model,the mechanical structure of the motor is simplified.According to the simplified structure of the motor,the nodes of the motor are divided.On the basis of uniform distribution of heat sources in the motor,without considering the circumferential heat flow and the independence of radial and axial heat conduction,the heat transfer process of the motor rotor,stator region and the whole motor in the operation process is analyzed.According to the basic principle of equivalent thermal circuit method and the equivalent thermal circuit model of hollow cylinder,the equivalent thermal circuit model of rotor,stator and motor whole area is established,and the calculation method of thermal resistance in the equivalent thermal circuit model is given according to the basic principle of heat transfer.Then,the heat source in the process of motor operation is analyzed.Since the proportion of stray loss is small,the calculation model of winding copper loss,iron loss and mechanical loss is established,ignoring the influence of stray loss.According to the basic size of the switched reluctance motor in this paper,the 2-D finite element electromagnetic field model of the switched reluctance motor is established in Flux software.The magnetic field distribution at different rotor positions is analyzed,and the characteristic region of the motor core is divided.On this basis,the finite element model of the motor under different working conditions is calculated,and the corresponding phase current waveform and magnetic density waveform are obtained.Then the copper loss and iron loss are calculated according to the loss calculation model.The calculation model of equivalent thermal circuit model of motor is established in MATLAB/Simulink,and the loss of each node is imported into the model as heat source.Then the temperature rise distribution of each node in the motor is calculated,and the temperature rise distribution is analyzed.Finally,the influence of water cooling system on motor temperature rise is studied and the reasons are analyzed.Then,a 2-D finite element thermal model of switched reluctance motor is established in Flux.The temperature rise of each point in the motor is calculated,and the reasons for the radial temperature gradient of different parts are analyzed.Considering the influence of axial heat transfer and heat dissipation at the end of the core,a 3-D finite element model of switched reluctance motor is established.The temperature rise of each point in the motor is calculated.The causes of the axial temperature gradient of different parts are analyzed.The maximum temperature rise of the nodes in the motor under different working conditions is calculated compared with the results of the equivalent thermal circuit model.On the basis of 3-D finite element thermal model,the influence of different polarity distribution on motor temperature rise is studied,and the reasons are analyzed.Finally,on the basis of three-phase 6/4 switched reluctance motor,an experimental platform is built.The temperature of motor windings under different working conditions was measured by the direct measurement method of temperature sensor.The results were compared with those of equivalent thermal circuit model and 3-D finite element thermal model.The accuracy of equivalent thermal circuit model and 3-D finite element thermal model was verified.