Research on an Inverter-fed Six-Pole Permanent Magnet Biased Magnetic Bearing

The configuration and working principle of a six-pole heteropolar permanent magnet biased magnetic bearing is introduced. And the mathematical models of the suspension forces are deduced through coordinate transformation. Then the paper studies the performances of the magnetic bearing for various area ratios between the permanent magnetic pole and the electromagnetic pole. The mathematical models are verified by finite element simulation. The results show that the current stiffness error rate between theoretical calculation and finite-element simulation is less than 3%, while the displacement stiffness error rate is much greater. A controller for this magnetic bearing is designed. To confirm the controller is effective, experiments were carried out with the proposed magnetic bearing system. The results all show that the rotor can be suspended steadily and the whole control system has good dynamic and static performance with robustness. Finally, power losses tests were done. As a result, the power losses of proposed six-pole magnetic bearing are only 9.85% of the traditional eight-pole active magnetic bearing for the same bias magnetic flux density.