Cage-rotor induction motor with unity power factor

The technique of using space transients in a linear induction motor in order to improve its power factor is extendable to the rotary induction machine. The transients take the form of phase jumps that cause the rotor to act as both generator of torque and as part exciter, in much the same manner as the DC winding of a synchronous machine. The technique involves novel stator winding arrangements and can be seen as an extension to the moving-coil regulator concept, whereby the short-circuited rotor acts not merely as an interphase coupling by mutual inductance, but as a combination of transformer and motional coupling. The phenomenon is clearly demonstrable in the action of a simple single-phase induction machine. A rewound conventional cage-rotor machine was tested and seen to deliver a large mechanical load while taking current at unity power factor. (See also LAITHWAITE, E.R., and KUZNETSOV, S.B.: IEEProc. B, 1981, 128, (4), pp. 190-194.)