Analysis of three-phase induction motors utilizing `The Iodekice Locus´-a normalized impedance circle

A method that allows students to analyze the performance of any three-phase induction motor operating at any arbitrary speed, either analytically or graphically, using the same conceptual approach is presented. The method uses a unity-diameter normalized impedance circle with a periphery calibrated in terms of normalized slip, which is defined as the ratio of per unit slip to a readily determined machine constant. Equations that allow the tabulation of the real and imaginery impedance components of the normalized circle as a function of normalized slip are developed. These data may be plotted for use with graphical analysis or used directly in a simplified mathematical analysis. The key factor in the development is shown to be the concept of normalized slip. Using this concept, the specific operating point of a machine can be simply and uniquely determined for any given value of per unit slip