State-space model for induction motors with static eccentricity faults

This work proposes a novel state-space model for eccentric induction motors, allowing the use of modern control theory to diagnose the eccentricity faults and to mitigate their effects. The proposed model is derived from the inductance-based multiple coupled circuit model. Instead of actual stator windings and rotor bars placed in slots, equivalent ideally distributed stator and rotor windings are considered in the motor modelling. The self and mutual inductances that incorporate the effects of static eccentricity in motors are evaluated using the modified winding function approach. Moreover, the rotor quantities are referred to the stator side to reduce the number of characteristic inductances. An eccentricity-oriented coordinate transformation is implemented to decouple the flux linkages in the new coordinate system and to reduce the system complexity further. Hereafter, stator currents and rotor fluxes are selected as system states, forming a fourth-order state-space model for the electromagnetic system of an eccentric motor. The proposed model is validated through comparisons with the reference data sourced from both the experiments and the finite element method. The potential of the proposed model for static eccentricity fault diagnosis purposes is explored.