Design, analysis and control of a new repulsive-type magnetic bearing system

A repulsive-type magnetic bearing system in which the radial bearing section makes good utilisation of the repulsive forces between the stator and the rotor permanent magnets results in a simplified axial control scheme. The authors report the design, analysis, fabrication and implementation of a new repulsive-type magnetic bearing system for a horizontal-shaft machine. The shape and configuration of the permanent magnet is the most critical component for satisfactory operation of this type of magnetic bearing. Modelling of the permanent magnets is done with the help of finite-element analysis and the nature of the repulsive forces and the stiffnesses are estimated along the three directions. Using the forces and expressing the rotor dynamics, the modelling of a real physical repulsive-type magnetic bearing system is discussed. The controller is configured around a digital signal processor. A prototype model has been designed and fabricated and experimental results are presented.