Research On AC Loss Characteristics Of Superconducting Permanent Magnet Motor Coil

Superconducting materials have excellent electrical properties due to their zero-resistance characteristics and Meissner effect,so they are widely used in electrical engineering fields,such as superconducting motors,large ships,power transmission and so on.Permanent magnet synchronous motor(PMSM)has the advantages of high efficiency and small volume.If its armature winding is made of superconducting material.its power density can be further improved to give full play to the advantages of both.For the superconducting permanent magnet motor,the coil AC loss is one of the key factors affecting its performance,so this paper studies the characteristics of the coil AC loss of the superconducting permanent m agnet motor.First of all,the development and basic theory of high temperature superconducting materials are summarized,and the research status of superconducting motors and AC losses at home and abroad is analyzed.The typical mathematical models of high temperature superconductors are compared and summarized as the theoretical basis for the subsequent simulation model construction and the research of AC loss characteristics.Secondly,the reason of superconducting strip loss and the mechanism of AC loss are analyzed.The analytical expressions for AC loss of single superconducting strip under different working conditions are summarized.According to the mathematical model of the superconductor has set up a finite element simulation model for the superconducting strip,through the finite element simulation of ac loss characteristics of superconducting strip under different working condition and its internal electromagnetic field distribution are analyzed,the ac loss and the electromagnetic field distribution is ob tained for the transfer current waveform,amplitude,frequency and the dependence of background magnetic field strength.Then,the analytical calculation formula of AC loss of superconducting coil is given.On the basis of the physical model of superconducting strip,a stack model of multiple strips and a two-dimensional axisymmetric model of multiple turns are built respectively to simulate the straight and bend regions of the racetrack coil.The characteristics of AC loss and the distribution of electromagnetic field in the superconducting coil under different working conditions are studied and analyzed by simulation calculation.Through analysis,it is found that the AC loss of the coil is related to the number of stacked layers,and there are some differences in the size of the AC loss on each layer.Finally,a superconducting experimental test platform was built according to the related theory of electrical measurement method.The critical current value of superconducting strip and the value of AC loss under corresponding working conditions were tested experimently,and the test results were summarized and analyzed.Through the comparison between the experimental data and the simulation results,the accuracy of the experimental measurement data and the feasibility of the experimental method are well verified,which lays a theoretical and practical foundation for the further research of AC loss and the optimization design of the superconducting permanent magnet motor.