Aalto University School of Electrical Engineering

In the rotating electrical machines, active magnetic bearing are basically performing the same role like mechanical bearings to support rotor. The function is based on the principle of magnetic levitation. The idea behind this involves creation of a magnetic field by supplying controlled currents in the bearing coil through amplifiers and complex power electronics. The accurate design of a magnetic bearing system incorporates many parameters before its implementation. The current work of the thesis encircles only the three dimensional (3D) modeling of axial active magnetic bearing (AMB). The static and dynamic models are analyzed for the bearing with a consideration of nonlinear material. In the study, the major emphasis is on the magnetic field, eddy current behavior and exerted magnetic forces in the magnetic bearing. The required input parameters for simulation are considered from the available two dimensional (2D) analysis for the same axial actuator. Elmer open source finite element tool is used in the entire work for making 3D simulations. Finally, the computed results are compared with the 2D case. As a part of the thesis work, a modified geometry is simulated to analyze eddy currents. The hypothesis in later task is the reduction of eddy current losses by providing a radial cut in the bearing ferromagnetic path. The radial cut brings asymmetry in the bearing and the three dimensional analysis provides the possibility to analyze the complete model. The results obtained in the above work provide a good understanding of 3D fields in axial AMB and the computed magnetic forces are in good agreement with the 2D results.