Transient and steady-state modelling of healthy and eccentric induction motors considering the main and third harmonic saturation factors

This paper deals with the modelling of magnetic saturation in induction motors (IMs) with particular focus on the equivalent or fictitious air-gap permeance technique. Besides, an improved version of this technique is provided so as to account for the transient starting process and the third harmonic saturation factor in addition to the fundamental one. This is for the symmetric case. Under air-gap eccentricities, extension of both saturation models is proposed using the varying saturation factor solution. The 2D-modified winding function approach (2D-MWFA) is the base of the inductance calculation and the state equations are derived from the well-known multiple coupled circuit model (MCCM). Thanks to such considerations, skew effect, rise of the magneto-motive force (MMF) across the slots, all winding harmonics, and many faulty states can be judiciously taken into account. In summary, five derived saturation models are discussed in favour of a good handling of the saturation phenomenon in cage IMs. The work is supported by extensive simulation and experimental results of eccentricity, broken rotor bar, and combined faults.