No load characteristics of a bearingless induction motor

This study involves a bearingless induction motor constructed with additional two-pole stator windings. These additional windings can be used to produce radial forces on the rotor shaft. The two-pole winding currents were regulated by radial position control loops to maintain the rotor´s position near the stator center. The voltage and current relationships of the two-pole windings were derived from a machine inductance model and equivalent circuits. The influence of secondary circuits was also taken into account. The theoretical values of current, voltage, and radial force were compared with the experimental results. It was found that the two-pole windings need only about 2% of the volt-ampere requirements of the main motor windings.<>