Research On Key Problems Of Mesoscopic Hysteresis Model Of Electrical Steel Sheet And Its Application

The electrical steel sheet in motor core has complex magnetic characteristics in the actual operation process,and fine simulation of the magnetic characteristics of electrical steel sheet is of great significance to improve the efficiency of electrical equipment and reduce energy consumption.At present,in order to improve the simulation accuracy of magnetic properties,scholars at home and abroad mainly carry out research from three perspectives: microscopic,mesoscopic and macroscopic.The representative Preisach hysteresis model from the macro perspective describes the hysteresis characteristics from the input parameters fitted with the experimental data,which belongs to the multi-parameter model of hysteresis theory.The microscopic level is based on the interaction among material atoms,so the calculation time of micromagnetic simulation is long,and it is difficult to describe the magnetization process in the macroscopic samples.From the mesoscopic point of view,the micro domain magnetization mechanism is integrated into the establishment of the macroscopic magnetic characteristic model,so the mesoscopic hysteresis model not only has microscopic properties,but also reflects the macroscopic phenomenon.Because it does not need a large number of experimental data,the calculation speed is fast.In this thesis,the key problems in the simulation of mesoscopic hysteresis model based on domain energy minimization are studied to improve the simulation efficiency and calculation accuracy of the model,which is helpful to promote the practical engineering application of the model.The details are as follows:Firstly,aiming at the problem of obtaining the local minimum of the magnetic domain energy equation,a variable step gradient descent method was proposed to locally minimize the total energy of the magnetic domain to obtain the unit magnetization vector of the magnetic domain.The study is carried out from the energy of each magnetic domain in the grain and the probability of domain distribution was expressed by means of Boltzmann distribution law.The effectiveness of the improved method was verified by the comparison of macrocopic hysteresis measurement experiments and mesoscopic magnetic simulation results.Secondly,aiming at the problem of demagnetization energy solution method,the influence of different solution methods on the simulation accuracy of mesoscopic hysteresis model were discussed.The key factors of solving demagnetization energy were discussed,and two methods of solving demagnetization energy were given.One was based on the interaction between magnetic dipoles,and the other was based on the macroscopic material size.Based on these two methods,the corresponding hysteresis model was established,and the simulation accuracy was compared.Thirdly,aiming at the simulation problem of local hysteresis loop of mesoscopic hysteresis model under harmonic magnetization,an improved STOP hysteresis model combined with mesoscopic hysteresis model was proposed.Based on the analysis of the key factors affecting the harmonic magnetic field of local hysteresis loop,the magnetic characteristics of electrical steel sheet under harmonic magnetization were simulated by using the improved stop hysteresis model and mesoscopic hysteresis model,and the effectiveness of this method was verified.Finally,the magnetic field simulation calculation model of an asynchronous motor was built,and the magnetic field intensity of the motor stator core node in one cycle was calculated.The obtained data was substituted into the mesoscopic hysteresis model,the hysteresis curve of the motor stator core was achieved,and the engineering application of the mesoscopic hysteresis model was realized.