ANALYSIS OF 3-PHASE INDUCTION-MOTORS UTILIZING THE IODEKICE LOCUS - A NORMALIZED IMPEDANCE CIRCLE

This paper 1 proposes an insightful method-utilizing a unity-diameter normalized impedance circle with a periphery calibrated in terms of normalized slip-which students may use to evaluate the performance of any induction motor operating at any arbitrary speed. Equations are developed which allow one to tabulate the real and imaginary impedance components of the normalized circle as a function of normalized slip. These data may be plotted for use with graphical analysis or used directly in a simplified mathematical analysis. The method was originally conceived for graphical analysis because of the ease with which efficiency measurements could be made. However, the same conceptual approach may also be used with a purely mathematical analysis. The key factor in the development is the concept of normalized slip s(n), which is defined as the ratio of per unit slip to a readily determined machine constant s(N). Using this concept, the specific operating point of a machine can be simply and uniquely determined for any given value of per unit slip.