Design Method Based On Asymmetry Factor of a Novel Three-Pole Magnetic Bearing

Asymmetric three-pole magnetic bearings (MBs) have higher power density and lower cost, compared to the symmetrical magnetic bearings with four poles or eight poles. This paper presents a new asymmetric three-pole structure with secondary air-gap for a radial magnetic bearing. Asymmetric permanent magnet (PM) biased MB can produce a static levitation force by bias magnetic flux. The secondary air-gap can ensure that the armature winding flux and PM flux are separated. The configures of the proposed MB are demonstrated. Analytical model with equivalent magnetic circuit method is deduced. The design method based on asymmetry factor is proposed for the three-pole MB (TPMB). The characteristics of the TPMB such as magnetic flux distribution and magnetic levitation force are analyzed by the finite-element method (FEM). The design values and FEM results are compared to validate the effectiveness of the presented design method.