Theoretical and Experimental Reevaluation of Short-Circuited Rotor Windings in Induction Machines

Squirrel-cage induction machines (IMs) have been widely used in industrial motor drives, automotive and aerospace applications. This paper presents the theoretical and experimental studies of short-circuited rotor windings in squirrel-cage IMs from the new perspective of air-gap magnetic field modulation. The modulation behavior of the short-circuited rotor winding, i.e., the squirrel-cage winding, has been analyzed analytically. It is revealed that the closed cage winding is equivalent to a set of equally-spaced isolated loops with the bar resistance and leakage inductance scaled. The rotor resistance plays an important role in the operation of IMs in contrast to its close relative-brushless doubly-fed IMs. The space-time relations in squirrel-cage IMs are also derived from the modulated stator MMF, which can be used to minimize the overall simulation time of transient electromagnetic finite element analysis (FEA) of IMs for high-fidelity reduced-order model extraction and noise, vibration and harshness (NVH) analysis. An experimental setup has been developed for testings and validations.