Radial and axial force calculation of BLDC motor with passive magnetic bearing

A new structure of brushless DC (BLDC) motor with passive magnetic hearings is introduced in this paper. The magnetic suspension of the rotor is realized by using the proposed passive magnetic bearings and does not need to be controlled. The axial stability of the rotor can be obtained by the radial force of the passive magnetic bearings and by the instinctive behavior of the PM motor in axial alignment of the stator and rotor. The radial magnetic suspension of the machine rotor can be realized by the optimal design of the air-gap length, thickness and axial length of the PM rings both of the passive magnetic bearings and the BLDC motor based on the accurate calculation of radial and axial forces.