Comparison of models of faulty induction motors: Performances and applications

This paper proposes a comparison of several circuit models of induction motors with broken bars in terms of representation of the phenomena, identifiability of its parameters as well as computing time. Such a comparison is rare as many papers focus on the presentation of new models. The three models studied in this paper are based on electrical circuit equations obtained using a common set of hypotheses which is important to reach the objectives. The different models are totally equivalent in healthy operations. A d-q stator transformation is used for the implementation of Model 1, a asymmetrical d-q rotor transformation is then added in the case of Model 2 and the application of the theorem of superposition leads to Model 3. Model 1 gives quite accurate results but requires extensive computing time and a precise knowledge of the rotor parameters. Equivalent performances are obtained with Model 2 but with a much lower computing time. The drawback is that the value of the d and q rotor resistances and inductances need to be numerically computed as they are functions of the slip. Finally Model 3 reaches less accurate results for high fault magnitude but in a low computing time and with few parameter knowledge as well as a good interpretation of the faulty machine behaviour. The three presented models cover then the complete range of applications, i.e. from the faulty machine test platform to the on-line diagnosis of machines.