Rotor-bar currents in squirrel-cage induction motors

Introduction THE rotor of a squirrel-cage induction motor is an extremely simple and rugged piece of mechanism; and due largely to this simplicity, it resists accurate analysis of its behavior by ordinary testing technique. Its design has been perfected by cut and try methods, making assumptions with respect to rotor current to simplify the theory; but the actual current in the bars has remained a mystery. The purposes of this paper are: first, to present oscillograms of rotor-bar currents; second, to extend the theory of induction motors to include the computation of rotor-bar currents; and third, to show the effect of the rotor current harmonics upon the efficiency of the motor.