Nonlinear Calculation of Active Magnetic Bearings Dynamic Magnetic Field by Finite Element Method

摘要

Active magnetic bearings' open-loop instability makes the features of dynamic magnetic field crucial to the control performance. We presented a nonlinear calculation of AMBs dynamic magnetic field by FEM. Firstly, we constructed a AMB's dynamic field FEM model considering the magnet's nonlinear permeability; Secondly, we applied a harmonic current to the coils through 160 load steps and a zero magnetic potential boundary condition; Finally the field was solved and magnetic flux lines, air gap flux density and eddy current density were retrieved and analyzed. Because of the nonlinearity of eddy current, air gap flux density is not standard harmonic and lags behind the source current, and as magnetizing energy equalizes eddy current losses, air gap flux density approaches harmonic.