Design and Basic Characteristics of Multi-Consequent-Pole Bearingless Motor With Bi-Tooth Main Poles

A multi-consequent-pole bearingless motor which is adapted to low speed rotation is presented. The bearingless motor can be used in swinging stages (or platforms) under specific conditions. Two degrees of freedom (2DOF) are actively controlled in the radial x-y directions. A gap sensor is required to control each DOF. Although 2DOF bearingless motors almost have a flat rotor so that axial length of the rotor is small, the device needs gap sensors and its target. In this paper, a novel stator structure is proposed and a design procedure considers the installation of the gap sensors on the stator. Three dimensional finite element analyses are carried out. An amplitude pulsation and a direction error of the radial suspension force with respect to the rotor rotational angular position are evaluated. Two machines with a conventional stator and the proposed stator are tested and compared. It is shown the proposed machine has beneficial performance by experimental verification.