Operation analysis of a three-phase induction motor with deep rotor bars and variable parameters

The paper presents a mathematical model of the three-phase induction motor (IM), whose rotor construction involves the presence of a squirrel cage executed with deep bars (DB). The model, detailed in dynamic and steady-state forms, covers the operation of the induction motor, energized from a constant frequency supply. Besides the steady state regimes, the model covers the analysis of transient regimes, such as starting across the line with or without reduced voltage starters and changes in load torque. The dependency on the frequency of the rotor parameters is still a vivid subject for researchers, leading to the development of multiple models validated by experiments over the years. The derivation of the model from this paper starts from a well-known space phasor model, modified by introducing the rotor parameters referred to the stator $R^{\prime}2(\omega_{r}),L^{\prime}2\sigma(\omega_{2})$, as functions of the rotor frequency f
r
, and consequently of slip, because of the skin effect and local saturation of the rotor slot’s neck. Following such an assumption validated by the literature, one developed slip-dependent analytical expressions of the rotor parameters referred to as the stator. The modified model became the subject of simulations whose outcome is assessing the steady state and transient characteristics of an induction motor. The obtained results verify the conclusions from multiple bibliographical resources.