Research On Key Issues Of High-speed Permanent Magnet Synchronous Motor Supported By Magnetic

Compared with traditional motors,high-speed permanent magnet synchronous motors can be directly connected to high-speed loads,and have the advantages of high efficiency,compact structure,high power density,small moment of inertia,and good dynamic response performance.In the process of high-speed operation of the motor,the mechanical loss of ordinary mechanical bearings is usually high,which greatly reduces the operating efficiency of the equipment.Therefore,the magnetic suspension bearing,which has the characteristics of no contact,no wear,no lubrication,high speed,and high precision,has been widely concerned in the field of high-speed motors.This article takes the magnetic suspension supported high-speed permanent magnet synchronous motor as the research object,and key issues such as high-speed motor design and analysis,high-speed motor rotor strength analysis,and radial-axial combined magnetic bearing design optimization are studied.The main contents are as follows:(1)Research and design are carried out on the main body of high-speed permanent magnet synchronous motor and its active magnetic bearing support system.First,the comprehensive design of a permanent magnet synchronous high-speed motor with rated power of 250kW and rated speed of 26000rpm is carried out,which includes the determination of the main dimensions,the selection of slot-pole coordination,and the design of the stator and rotor structure,selection of various parts of materials,etc.The electromagnetic analysis of the designed high-speed motor is carried out with finite element simulation software,including no-load characteristic analysis and load characteristic analysis.Secondly,using various losses of the motor as the heat source,the temperature field analysis was carried out to verify the effectiveness of the design.Then the design and analysis of the active magnetic bearing supporting the motor’s levitation rotation are carried out.At last,the prototype of the magnetic suspension supporting high-speed motor was trial-produced.(2)The structural strength of the rotor of high-speed permanent magnet synchronous motor is studied by combination of theoretical analysis and finite element verification.First,the strength of the surface-mounted rotor magnet structure of the high-speed permanent magnet synchronous motor is theoretically analyzed and studied.Taking the high-speed motor designed in the article as an example,analysis calculation of the rotor stress is performed.Then,the finite element method was used to simulate the strength of the rotor,which was compared with the theoretical analysis and calculation.The comparison verified the accuracy of the analytical calculation and the simplicity of the rotor design calculation.Next,based on the analytical model,the GUI calculation software of rotor strength is established,which greatly simplify the design process of the rotor sheath.Finally,the influence of rotor stress with temperature,speed,static interference,thickness of protective sleeve and other factors is analyzed in detail.(3)The new combined radial-axial combined permanent magnet bias magnetic bearing is analyzed and studied based on the magnetic circuit model and three-dimensional electromagnetic field finite element analysis and optimization design research.Compared with ordinary radial magnetic bearing and axial magnetic bearing split application,although the structure of the radial-axial combined hybrid magnetic bearing is more complicated,it is small in size and low in cost.It has a good application prospect in the field of high-speed motors.First of all,this paper analyzes the structure and principle of a new type of radial-axial combined magnetic bearing,and uses compensation coil to solve the problem of magnetic flux imbalance in the magnetic bearing control.Then considering the influence of the magnetic bearing leakage and the non-linear permeability of the iron core,a more accurate magnetic circuit model is established for the magnetic bearing,and on this basis,the electromagnetic force was calculated analytically.The comparison with the finite element verifies the accuracy of the analytical calculation and greatly simplifies the design of the combined magnetic bearing.At last,based on the magnetic circuit model,the radial and axial bearing capacity and volume are optimized under the premise of satisfying the constraint conditions of slot full rate and magnetic density,and the particle population optimization algorithm is used to calculate the main design parameters of magnetic bearings.Target optimization,thereby obtaining the optimal design,and using finite element analysis software to verify the optimization effect.