Low rotating loss 2-pole radial magnetic bearing biased with permanent magnet

A new structure of radial magnetic bearing biased with permanent magnet (RPMB), so called 2-pole RPMB is proposed. Based on the original idea, the reduction of flux fluctuation frequency in rotor core to reduce the rotating loss of conventional 4-pole RPMB, 2-pole RPMB has similar structure except the pole-number, which is only half. Based on the measurement of material alternating-loss of rotor core, it is estimated that 2-pole RPMB could reduce rotating loss more than half than 4-pole contrast. To verify the effect on loss reduction, the experiment was carried out based on two magnetically suspended flywheels for energy storage and attitude control on satellite, equipped with 2-pole RPMB prototypes and 4-pole contrast respectively. It has shown that 2-pole RPMB reduced rotating loss by more than 0.85W at the normal speed 30000rpm on both radial and axial supporting statuses, i.e. 14% of flywheel run-down loss with 4-pole RPMB without losses separation. Though the current stiffness of 2-pole RPMB prototype is 23% less, it reduced the total losses because copper loss is small originally due to permanent magnet bias field. Further, during the high speed and large power applications, the loss reduction of 2-pole RPMB would be more meaningful.