Electromagnetic Characteristic Analysis And Temperature Field Calculation Of 100kW High Speed Induction Motor

The rotor structure of high-speed induction motor(HSIM)is simple and its mechanical strength is high.It has unique advantages in the application of high-speed motor.Overseas countries have accumulated many years of research experience in the field of HSIMs,while domestic research foundation is relatively weak.In this paper,some basic problems of a 100 kW,25000 rpm high-speed induction motor will be studied.The main work is as follows:Firstly,the constant V/F starting process of open-loop speed of HSIM is analyzed.Using T equivalent circuit of induction motor,the speed-time(n-t)curve of general induction motor under full voltage start-up is deduced.It is considered that the speed of HSIM is on n-t curve of each frequency point during constant V/F start-up.Based on this,the n-t curve of the whole frequency conversion starting process of HSIM is calculated,and the results are in good agreement with the Simulink values.The limit value of frequency rise rate under the constraint of mechanical characteristic curve of motor is given by calculation.Secondly,starting from the relativity of electromagnetic theory,analogizing the magnetic circuit method and using the concept of potential and Gauss law,the electric field distribution in the air gap of AC motor under the new reference system is discussed,the expression of electromagnetic torque of AC motor is given.The understanding of electromagnetic relations in motors is deepened.Thirdly,the calculation of motor stator core loss is focused on.Based on the orthogonal decomposition calculation model of motor core loss,a discrete calculation method is proposed.With the post-processing function of the finite element software,the hysteresis loss,classical eddy current loss and excess loss are calculated directly by using the results of magnetic field calculation.The results show that the calculation method has a certain reference value.Last,on the basis of the loss calculation results,a two-dimensional temperature field analysis and calculation model for water cooling of motor is established by combining the analytical method with the finite element method.It's confirmed the trend of convection heat transfer coefficient between cooling water and waterway by analytical method.The convection heat transfer coefficients are given to the two-dimensional solution model as the boundary condition to solve the problem.This method reduces the dimension of three-dimensional temperature field distribution,simplifies the calculation process and ensures the rationality of the model.From the experimental results and model calculation results of the prototype,the model has certain practicability.