Development of a Passive Magnetic Bearing System for a Flywheel Energy Storage

Magnetic bearings are an attractive alternative to mechanical bearings in flywheel energy storage systems since they greatly reduce friction and wear. However, new problems are introduced in terms of stabilization; particularly the magnetic bearing must provide enough damping to reduce excessive vibrations. Two novel configurations of passive magnetic bearings are introduced to meet system requirements. The first configuration, utilizing two Halbach arrays, is proposed to introduce a levitating force as well as lateral stability. The second configuration uses a null-flux coil passive magnet array to add lateral stability. This paper will focus on lateral stability. Displacements in the lateral direction will result in a correction of rotor motion based on its velocity. In this work, firstly the configuration of the Halbach and null-flux coil arrays is presented. Finite element models are then developed for both cases to investigate the resulting magnetic field, its reaction to rotor velocity, and its effects on the system. As a result, it shows the effectiveness of the proposed configuration to stabilize the lateral dynamics of a flywheel energy storage system.