Transfer Characteristics of Radial Force of Induction-type Bearingless Motors with Four-Pole Rotor Circuits

Rotor winding configurations have been proposed for induction type bearingless motors. Con ventional squirrel cage rotor windings can been seen as not only 4-pole path but also 2-pole path. Th us, a part of curren tin 2-pole radial force windings flows into the squirrel cage rotor windings, which results in decreased radial force and serious phaselag. Two rotor windings are proposed, which can been seen as 4-pole winding only. Secondary resistances are calculated and compared with measured values. These values are sHghtly high if rotor-bars are the same diameters. The phase-lags of two proposed rotors are found to be significantly smaller than those of the conventional squirrel cage rotor. Successful high speed operations are realized.