Fabrication of a repulsive type magnetic bearing using a novel arrangement of permanent magnets for rotor suspension

In repulsive type magnetic bearing system usually the rotor is levitated by the repulsive forces between stator and rotor permanent magnets. The system is unstable in nature. The controlled electromagnet is used to keep the rotor in the desired position. The repulsive magnetic bearing system has the advantages of using a smaller number of electromagnets and simplified control scheme compared to active magnetic bearing system. The advantages of using magnetic bearing system compared to mechanical bearing in high speed motors are long life, frictionless and lubrication free operation, feasible operation at high speed etc. Two repulsive magnetic bearing systems using permanent magnets for the levitation were fabricated a few years back and their levitation and control performance were compared. Material characteristics and configuration of permanent magnets are the central component for this type of bearing system. Due to aging and/or as both the magnets are repelling each other, there will be demagnetization of the permanent magnet, resulting the field distribution along the magnet's periphery non-uniform and this will affect the performance of the bearing system.