Analysis and Experiment of a 6-phase Bearingless Induction Motor

Conventional bearingless motor has two sets of 3-phase stator windings. The main winding is used to produce torque, while the suspension winding is utilized to produce radial force. This paper proposes a new multiphase bearingless machine with a single set of multiphase windings, taking advantage of the multiple control degrees of freedom in multiphase machine. Two groups of currents are fed to the single set of multiphase windings to produce torque and radial forece. Taking a six phase induction motor for example, the inductance matrices, considering air gap eccentricity, are calculated with the Modified Winding Function Method. The mathematical model of the new bearingless machine is set up, and the radial force analytical model is deduced by virtual displacement. The control algorithm based on rotor flux-orientation of "motor currents" is presented. Experiment results verified the feasibility of this new bearingless motor.