The operation of three-phase induction motors with unsymmetrical impedance in the secondary circuit

The operation of an induction motor at one-half normal speed against appreciable load, by means of unbalanced impedance in the secondary circuit, is shown to be a practicable possibility with accurately predictable characteristics. Precautions must be taken to prevent saturation of the main magnetic circuit of the machine, and in some cases it may be essential to limit the injection of low-frequency currents into the supply system. Simple solutions to these problems are described, and it is concluded that the method has sufficient merits to justify its use in certain applications where a speed reduction to about one-half the normal value is required.