Research On Isolated Rotor Type Electromagnetic Bearings System

Compared with traditional mechanical bearings,electromagnetic bearings have the characteristics of no contact,no wear and long service life,and they have broad application prospects in the industrial field.In this paper,the bearing itself and the displacement sensor are studied by using the electromagnetic bearing which is applied to the control rod drive mechanism and the stator and rotor need to be isolated.Firstly,the structure and working principle of the radial electromagnetic bearing are analyzed.The mathematical model is deduced by the magnetic circuit method,and the significance of the current stiffness coefficient and displacement stiffness coefficient is explained.Then the finite element simulation software Ansys Maxwell was used to model and simulate the electromagnetic bearings.The effects of the arrangement of the magnetic poles on the presence or absence of layers of the magnetic bearing are analyzed,including the magnetic flux path,the magnetic flux density of the air gap,and the size of the electromagnetic force.The non-superposition of the electromagnetic force when the rotor is eccentric is illustrated.The relationship between the electromagnetic force and the control current,the relationship between the electromagnetic force and the displacement are analyzed;the electromagnetic force received by the rotor is simulated when the different layers of permeability are used respectively.The change law of maximum bearing capacity with magnetic permeability of the interlayer was analyzed.Next,the working principle of the differential transformer type displaceme nt sensor was analyzed,and the corresponding mathematical model was established.The finite element modeling was performed in Ansys Maxwell.The magnetic permeability and conductivity of the layers were simulated respectively,and the conclusion was drawn that both permeability and conductivity of the layers could affect the sensitivity of the sensor.Finally,according to the prototype,an experimental platform was set up to test the output of the sensors at several different positions of the rotor.This effectively verified that the differential transformer can still reflect the changes in the position of the rotor through changes in the output voltage when there are layers between stator and rotor.