Analysis of no-load characteristics of a bearingless induction motor

This paper presents the design and analysis of a bearingless squirrel cage induction motor. There are two sets of stator windings. The main winding is a four-pole arrangement, while the control winding is a two-pole type. The latter is utilized to produce radial forces on the rotor shaft. The two-pole winding currents are regulated by radial position sensors and control strategies in order to maintain the rotor shaft position near the air gap center. The voltage and current relationships of the two-pole windings were derived from the machine inductance model and equivalent circuits. The influences of the secondary rotor circuits were also taken into account. The theoretical values of current, voltage, and radial force were compared with experimental results. It was found that the two-pole windings need only about 2 percent of the voltampere (VA) requirements of the main motor windings