Modelling dynamic eccentricity in smooth air-gap induction machines

In this paper a general model of machines with dynamic eccentricity is developed, using permeance harmonic analysis. The variation of the machine inductances is calculated and the different types of machine models are examined. A general treatment for modelling dynamic eccentricity in smooth air gap machines is developed. It is shown that the primitive fault mechanism can be modelled using modulation of the stator inductances at twice the rotational velocity of the rotor and that the rotor parameters depend on their spatial position with respect to the minimum airgap. On the basis of the derived model some numerical calculations are presented for the transient runups of healthy and faulty machines. For verification a series of experiments were conducted on a specially made 11 kV test machine and are illustrated in the paper.