Bidirectional homopolar magnetic bearings with fault tolerant capability

Abstract

A fault tolerant current distribution scheme is presented for a bi-directional magnetic bearing with reduced eddy currents and cross coupled stiffness. The bearing continues to function normally even though one coil among four radial coils and one coil of two axial coils fail. The dynamic properties and load capacity remain unchanged for the suggested fault tolerant control scheme at the cost of additional hardware such as a decoupling choke, additional DSP channels, and power amplifiers. A one-dimensional circuit that represents the bi-directional bearing is utilized to obtain the optimal bearing parameters such as the radial pole face area, number of coil turns, and permanent magnet size.