The Structure Design Of Active Magnetic Bearing And The Characteristic Analysis Of Magnetic Field And Force

The magnetic bearing uses controllable electromagnetic force to realize the full-process non-contact between the supporting parts and the rotating shaft during the operation of the motor system.The design process applies electromagnetic,mechanical and computer control and other disciplines.Electromagnetic field analysis is the basis of active magnetic bearing loss analysis,and rotor force analysis is the basis of magnetic bearing performance analysis.The reliability of active magnetic bearings in operation is also very important.The main work done in this thesis is as follows:(1)Starting from the simplified magnetic circuit model of the active magnetic bearing,the basic principle of the active magnetic bearing is analyzed,and the electromagnetic force generated by the single el ectrode of the bearing is derived from the principle of virtual displacement.Then from the perspective of engineering design,a three-phase asynchronous The motor designs a five-degree-of-freedom active magnetic bearing support system for the drive motor.Considering the size constraints of actual processing and assembly,the optimization design method of radial and axial active magnetic bearing structural parameters is deduced and the design is verified by the finite element method.Finally,Perform physi cal hardware assembly.(2)According to the rotation state of the magnetic bearing rotor,the vector magnetic potential is introduced,and the vector magnetic potential equation of the magnetic bearing is derived.A simulation model of an eight-pole radial magnetic bearing is established,and the distribution of the bearing magnetic field and force at each speed is obtained through simulation.Four closed paths are set at different radial depths inside the rotor as the measurement reference line.The magnet ic density distribution curve is subjected to harmonic decomposition,and the change rule of the proportion of each harmonic of the magnetic density with the speed is obtained;the distribution curve of the radial magnetic density and the tangential magnet ic density with the speed of the rotor surface is obtained by simulation,and the distribution curve of the rotor surface Harmonic decomposition of the radial flux density curve is carried out,and the distribution characteristics of the proportion of each harmonic of the radial flux density with the speed are obtained;the distribution characteristics of the suspension force density and the drag force density on the rotor surface with the speed are obtained by simulation,and the distribution characteristi cs of the rotor surface The suspension force density curve is subjected to harmonic decomposition,and the distribution characteristics of the proportion of each harmonic of the suspension force with the rotation speed are obtained.The power loss caused b y the eddy current is deduced from the drag force density distribution curve with the rotation speed.(3)Aiming at the equivalent magnetic circuit of the eight-pole radial active magnetic bearing,the matrix reflecting the connection of the coils and the current distribution matrix are defined,and the linearization principle of the electromagnetic force and the control current in two degrees of freedom is derived.The fmincon function is used to obtain the current distribution matrix of the bearing when t he coils are normal and the two disconnection faults.The fault-tolerant control method of the reconstruction current distribution matrix of the eight-pole radial bearing is studied,and the fault-tolerant control effect of this method is tested by simulat ion.The simulation results show that the method can meet the fault-tolerant control requirements of the rotor in the fault state.