Integrated radial/thrust magnetic bearing without thrust disk for a high‐speed driving system

Abstract

In this paper, the authors present a novel compact structure of an integrated radial/thrust magnetic bearing (IRTMB) without thrust disk. The structure without thrust disk can further reduce the frictional and windage loss for a high-speed driving system. At the same time the rotor supported by the two IRTMBs can further reduce its axial size, and improve rotor dynamic performance. The axially magnetised magnet forms a cylindrical magnet sandwiched between a four-leg laminated radial stator and a solid return pole piece. On the basis of the return pole, a novel air gap, called the return air gap, is constructed between the rotor and the return pole. The bias flux produced by the permanent magnet and the control flux produced by the thrust magnetic bearing (TMB) unit are conducted by this return pole. The magnet produces the bias flux for radial and TMB units, and separates the control flux loops of radial and TMB units. The IRTMB structure and its analytical models are deduced using equivalent magnetic circuit method. To study the performances of the IRTMB, another IRTMB with thrust disk used in a high-speed motor with power of 45 kW at 60,000 rev/min has been fabricated and is chosen as the comparison target.