Fault Tolerance of a Lorentz-Type Slotless, Self-Bearing Motor According to the Coiling Schemes

ermanent magnet (PM) self-bearing motors provide independent bearing and motor functionality in a single magnetic actuator. Typical designs have used slotted stators and thin surface mounted PM's in order to provide a minimum reluctance path for the bearing control flux such that adequate bearing forces are generated. Such designs necessarily result in smaller torque production due to the thin PM's and have large torque ripple due to the slotted stator. This paper introduces the principles of motoring torque and bearing force of the slotless thick PM's self-bearing motor and the proposes a new coil winding method to minimize the effect of coil failure without any redundant devices. Comparisons of the stiffness and stability characteristics between typical and proposed coil winding methods are presented. The analysis indicates that the proposed coil winding method can minimize the coil failure effects and the motor can levitate and rotate stably in spite of the coil failure.