Induction Machine Instability Predictons - Based on Equivalent Circuits

Induction machine instability is predicted on the basis of equivalent circuits. The circuits are derived assuming sinusoidal perturbation of the rotor speed. Classic rotating field concept is used in the analysis. It is shown that equivalent estimates of the critical supply frequencies, at which instability occurs is obtained by the method shown in the paper and conventional eigenvalue analysis. Approximate, conservative analytical expressions are also obtained by using certain simplifying assumptions. It is possible to obtain the sensitivity of the instability region to different machine parameters. This indicates the parameter which has the greatest influence on stabilizing the machine. The approach developed may be extended to study the effect of time harmonics on the stability of induction machines.