Influence of Rotor Vibration on Magnetic Field Distribution of Radial Active magnetic Bearings

Coil currents of active magnetic bearing (AMB) change with the radial displacement of the rotor caused by rotor vibration, which affects the magnetic field distribution of the AMB. In order to analyze the influence of rotor radial vibration on the power loss of AMB, it is necessary to establish a relationship model between the magnetic field distribution characteristics and the rotor vibration. Considering the nonlinearity of the ferromagnetic material and the edge effect of the magnetic poles, the PID control method is used to control the currents of the stator coils in real time according to the vibration displacement of the rotor, and the nonlinear equivalent magnetic circuit model of the AMB considering the rotor and stator reluctance is established. The magnetic field distribution characteristics of AMB during rotor vibration are analyzed, and the magnetic density in air gap is obtained, and compared with the results given by the electromagnetic field finite element software. The error between the magnetic path method and the FEM analysis result is within 3%, Which has high accuracy. The model established in this paper provides a theoretical basis for the magnetic field analysis of the AMB during rotor vibration and the subsequent loss analysis.