Research And Optimization Analysis Of 3D Steady-state Temperature Field Of MW-level Permanent Magnet Generator

The progress of permanent magnet technology has led to a new trend of motor development.Compared with the traditional electric excited magnet generator,the permanent magnet motor is without devices such as brushes,excitation windings,collector rings and so on.It is simpler in structure and convenient for production and maintenance.In addition,it has the advantages of no excitation loss and high power factor.Inevitably,however,the motor will generate losses which performs in the form of heat during operation.Continuous high temperature will lead to demagnetization of permanent magnet on rotor or irreversible loss of magnetism and insulation aging and short circuit phenomenon.Once the permanent magnet motor loses magnetism,the output voltage of the motor will drop,which will cause great impact on the operation of the parallel power grid.Therefore,accurate calculation of motor temperature field is necessary to ensure the continuous and reliable operation of the motor.With the continuous improvement of economic level,the development of wind turbines tends to be in the direction of large capacity.The increase in singlegenerator capacity is based on the increase in online load.Large line loads result in more losses.More timely and effective transfer of heat generated by the loss becomes an important part of the motor design process in order to avoid motor damage or stop running.In order to solve the above problems,this paper takes a 6MW permanent magnet generator as an example,based on the theory of heat transfer and computational fluid mechanics,combined with the flow-heat coupling mechanism,and according to the actual cooling structure of the motor to establish the mathematical and physical model of the three-dimensional coupling field.At the same time,the basic assumptions and calculation boundary conditions are given,and the fluid flow and temperature distribution in the coupling field are analyzed by finite volume method.For the calculation results of the fluid field,the variation characteristics of the fluid velocity in the stator ventilation channel,the flow variation trend in each ventilation channel and the heat dissipation factor at the stator core boundary are analyzed in detail.For the calculation results of temperature field,from the global point of view,the overall temperature rise trend of the motor is analyzed,and combined with the fluid field analysis of cooling gas heat transfer process,the main heating components(winding,stator core,rotor pole and permanent magnet)are analyzed in detail.On this basis,the structural optimization scheme is designed,and the structure under different schemes is simulated and calculated,so as to find the most suitable ventilation structure.