Date of Award

Summer 2003

Document Type

Thesis - Restricted

Degree Name

Master of Science (MS)


Mechanical Engineering

First Advisor

Demerdash, Nabeel A. O.

Second Advisor

Yaz, Edwin E.

Third Advisor

Brown, Ronald H.


The multiple coupled circuit approach is traditionally used in designing control systems for squirrel-cage induction motors. In this approach, the rotor is represented by coupled rotor loops (circuits), each of which contributes a state variable to the whole model. Consequently, this increases the difficulty of directly using such detailed models in adjustable speed drive (ASD) control systems analysis and design due to the resulting large number of rotor related state space variables. The conventional d-q transformation and resulting equivalent circuit representation, though providing relatively simplified models to simulate the behavior of squirrel-cage induction motors, can only include the fundamental components of winding mmfs and flux density waveforms. That means higher order space harmonic effects on the winding inductances, due to a machine's physical configurations, are necessarily neglected. In this thesis work, this author presents a systematic approach to the determination of an ABC-based equivalent 3-stator-phase/3-rotor-phase (3-3) wound-rotor type induction motor representation to a 3-phase, P-pole, Nb-bar squirrel-cage induction motor, whose various inductances include the space harmonic components due to the geometric characteristics of the machine. These space harmonic inductance terms can be obtained from the winding function-winding distribution method. It is shown in this thesis that this "virtual" equivalent 3-3 wound-rotor type induction motor representation has exactly the identical motor performance characteristics as the original P-pole, Nb-bar squirrel-cage induction motor model. Meanwhile, this simplified 3-3 equivalent model has greatly reduced the number of the state space variables and has led to much shorter simulation times compared with the original squirrel-cage induction motor model. Hence, this modeling approach and formulations can be useful during the motor-drive systems design stage, and for overall control strategy assessment and practical applications. In a practical case study, a l.2hp, 2-pole, 34-bar, squirrel-cage induction motor was simulated using this equivalent model, and compared with the previous simulation results based on the TSCFE-SS modeling and experimental test results for the same case study squirrel-cage induction motor. These comparisons are very favorable and hence verify this thesis model equivalence.



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