Mathematical Model of Radial Suspending Force for a New Stator-Permanent Magnet Bearingless Machine

In this paper, a new stator-permanent magnet (PM) bearingless machine (SPMBM) is proposed. Its suspending windings, armature windings, and PMs are in the stator, while no PMs or windings are in the rotor. However, it is the focus in establishing an accurate mathematical model of radial suspension force to levitate the rotor stably by directly and effectively controlling the rotor eccentric displacement. First, operating principle and air-gap flux density distributions of the SPMBM are analyzed in detail. Then, an accurate mathematical model of radial suspension force is deduced by the Maxwell stress tensor method, and it is verified by the 2-D finite-element method (FEM). Results are consistent both by the radial suspension force mathematical models of the SPMBM and FEM.