Research On Key Problems Of New FeCo Based High Speed Permanent Magnet Motor

As a new type of permanent magnet(PM)material,FeCo based has lower temperature coefficient and higher thermal expansion coefficient than Nd Fe B PM material.It has great theoretical significance and engineering practical value in the development of high-speed permanent magnet motor.For this reason,this dissertation mainly aims at the advantages of FeCo based material properties,and designs and explores the performance of the new FeCo based High Speed Permanent Magnet Motor(FeCo based HSPMM)in the aspects of electromagnetism,loss,heat transfer,mechanical stress,rotor dynamics,vibration and noise,Using the Finite Element Method(FEM)and Analytical Calculation Method(ACM)as the main research means,we learned the specific advantages of Fe-Co based materials in the performance of efficiency motors,aiming at exploring and comprehensively developing high-speed permanent magnet motors with high power density,high efficiency and high reliability.(1)Exploration and research on the internal loss and temperature rise distribution of HSPMM with FeCo based materials;First of all,the curves of residual magnetism and intrinsic coercivity versus temperature for FeCo based and Nd Fe B permanent magnet materials are compared,and the structural parameters of a new type of FeCo based PM motor are designed based on the motor theory,considering the electromagnetic and mechanical strength constraints;Secondly,the 2D electromagnetic field model of PM motor with FeCo based and Nd Fe B PM materials is constructed,and the curves of the magnetic density of permanent magnet and the radial air gap magnetic density amplitude of the motor varying with temperature under different ambient temperatures are compared,and the advantages of FeCo based materials in electromagnetic field are pointed out;At the same time,the analytical method and the finite element method are used to solve the internal iron loss,winding copper loss and rotor eddy current loss of the FeCo based permanent magnet motor,and the correctness of the deduced loss analytical method is verified;In addition,the 3D model of air friction loss on the rotor surface is built,and the change curve of friction loss is obtained from the angle of motor speed,fluid axial speed,rotor outer diameter and air gap length;At the same time,a no-load test loss separation method is proposed to correct the accuracy of the simulation results,and the calculation reliability of the proposed loss separation method is verified through the electromagnetic parameter detection experiment of the prototype;Finally,based on the CFD method,the 3D temperature field model of FeCo based PM motor is built to explore its internal fluid velocity and temperature distribution,and the temperature rise detection platform of the prototype is built to verify the correctness of the above temperature rise distribution calculation.(2)Exploration and research on the strength of HSPMM rotor system made of FeCo based materials;Based on the principle of thick-walled cylinder,the unified analytical equations for strain field,displacement field and stress field of FeCo based PM rotor are derived;The analytical and finite element methods are used to check the rotor strength of the rotor system made of FeCo based and Nd Fe B under different working conditions,and the stress values of the titanium alloy sleeve and the permanent magnet under three working conditions of normal temperature static,normal temperature high speed and hot high speed are compared to verify the feasibility of the proposed analytical equation,and it is pointed out that the strength of the FeCo based PM rotor is superior;In addition,based on the derived stress analytical equation,the influence curve of static interference,sleeve thickness,thermal expansion coefficient of permanent magnet and shaft material on the rotor strength is obtained.Finally,the correctness of the above analytical and finite element calculation results is verified by the stress detection test of the prototype at1.2 times of the rated speed.(3)The research of FeCo based materials on the resonance of HSPMM when the working speed coincides with the critical speed;The analytical formula derivation of FeCo based rotor modal calculation,the construction of rotor dynamics finite element simulation model and the establishment of prototype rotor dynamics parameter detection platform were carried out respectively.The correctness of the proposed modal analysis and numerical calculation was verified through the error comparison analysis of three groups of data;Secondly,the three-dimensional FEA model of the critical speed of the FeCo based PM rotor system is constructed,and the critical speed and campbell diagram of the FeCo based rotor system with and without impeller are obtained.The relationship curves between the rotor outer diameter,rotor axial length,gyroscopic effect and the critical speed supported by the bearing stiffness are obtained respectively,pointing out that the FeCo based PM rotor has superior mechanical performance;Finally,through the vibration test of the prototype,the correctness of the calculated results of the dynamic model of the rotor system is verified.(4)Research on the vibration and noise of HSPMM with FeCo based materials;Starting from the rotor structure optimization and vibration noise suppression of the new FeCo based PM motor,based on the stress equation theory,the radial electromagnetic force of the stator teeth of the new FeCo based HSPMM is derived and analyzed,and the correctness of the analytical method is verified by using the multi physical field coupling method.At the same time,the radial electromagnetic force values of each order and frequency of the new FeCo based HSPMM are learned;In addition,the simulation model of electromagnetic vibration of the stator of the FeCo based amorphous alloy Metglas2605 is established considering the spatial distribution of the radial electromagnetic force of the motor and the electromagnetic vibration of the stator of the iron based amorphous alloy Metglas2605.The harmonic response calculation and modal analysis of the electromagnetic vibration of the new high-speed FeCo based PM motor are carried out.The waterfall diagram of the acceleration vibration noise of the optimized high-speed FeCo based PM motor at full speed is obtained.It is pointed out that the FeCo based PM rotor has superior performance in vibration and noise;Finally,the correctness and effectiveness of theoretical derivation analysis and finite element simulation calculation are verified through the prototype experiment of a new FeCo based PM motor.(5)In view of the problem that the comprehensive optimization design process of the new FeCo based HSPMM needs to be improved,starting from the structural parameter design of the new FeCo based HSPMM,the range of motor structural dimensions is obtained by using electromagnetic constraints and mechanical design theory;Secondly,the influence of design parameters on the loss,stress,temperature rise and vibration noise of the rotating rotor is analyzed in detail,including the influence of bearing stiffness,impeller mass,rotor diameter,rotor core length and gyroscopic effect on the critical speed,so as to learn the objective function and constraint box of the multi-objective optimization design of the new FeCo based HSPMM with multiple physical fields,NSGA-II algorithm is used to optimize the design of the new FeCo based HSPMM,and the comprehensive optimization design flow of the new FeCo based PM motor coupled with the specific NSGA algorithm and multiple physical fields is given;Finally,a new high-speed FeCo based PM motor with a rated power of 100 k W and a rated speed of 18000r/min was manufactured,and the correctness and effectiveness of the comprehensive optimization design process were verified through prototype testing.