An Analysis of a Prototype Permanent-Magnet Bearingless Motor using Finite Element Method

An analysis is done for a prototype permanent magnet bearingless motor. A Finite Element Method program is employed to see the influence of demagnetization of permanent magnets. Several critical parts of rotor magnets are made clear for both torque and radial force generations. It is found that tile most serious demagnetization occurs at the permanent magnet located at an edge of rotor poles. At this point, torque and radial force currents are the maximum. Moreover, it is shown that the serious condition occurs when the direction of the radial force flux is oriented so that negative mmf is imposed to the permanent magnet at the pole edge. The location of a critical permanent magnet and current conditions are made clear.