Electromagnetic Field Analysis And Optimization Design Of Radial Magnetic Bearing

Magnetic bearing is a novel bearing with superior bearing performance which uses electromagnetism to suspend the rotor in space to realize the non-contact support between the stator and the rotor.With the advantage of unlubricated,little oil contaminated,long life-span and the adaptability of various environment,magnetic bearing is an ideal choice for high-speed motor bearing.As the high speed permanent magnet synchronous motor with rated power of 24 KW and rated speed of 72000r/min for the application background,and combined with the model of the prototype's rotor system,this thesis mainly focuses on the structure design for the radial active electromagnetic bearings.Meanwhile,in order to improve the bearing capacity of RMB while loss,critical speed and control stiffness are considering,the structural dimensions of the magnetic bearing should be optimally designed.Firstly,the mathematical model of electromagnetic force of radial magnetic bearing is established based on equivalent magnetic circuit method,and the influence of structural parameters and control parameters on electromagnetic force is analyzed based on the mathematical model.According to the performance parameters of the prototype system,the structural parameters of the radial magnetic bearing are determined.Secondly,based on finite element theory,according to the structure parameters and control parameters,a finite element simulation model of homopolar and heteropole radial magnetic bearing are built.Through the finite element simulation,the variation of levitation force and eddy current loss of radial magnetic bearings with control current is analyzed,and the paper proves that magnetic field coupling and eddy current loss of homopolar radial magnetic bearing smaller than heteropole radial magnetic bearing.Finally,this paper introduced the basic principle of fruit fly optimization algorithm,multi-objective processing technology and constraint processing technology.According to the optimization demand,the optimization objective function,constraint condition and optimization variables of radial magnetic bearing are given.In this paper,the fruit fly optimization algorithm is introduced into the optimal design of RMB for high speed motor.The size parameter of RMB is taken as the optimization variable,and multi-objective optimization is carried out with the aim of optimizing bearing capacity,volume and axial length.The optimization results are analyzed by finite element simulation,and the effectiveness of the optimized algorithm is verified.