Small-signal transient analysis of induction machines with stator inter-turn faults using dynamic phasors

This paper presents a dynamic phasor modeling approach to the small signal transient analysis of induction machines with stator inter-turn faults. An important advantage of dynamic phasor modeling is that it results in time-invariant models of unbalanced three-phase systems. The linearized dynamic phasor model facilitates the analytical studies of transients of unbalanced systems using eigenvalues. The linearized q - d model of a machine with stator inter-turn fault has a system matrix having time periodic entries, and is thus unsuitable for eigenvalue analysis. The dynamic phasor model helps in this case. In this paper, the dynamic phasor model of induction machine with stator inter-turn fault is developed, and this is further used for eigenvalue analysis. The eigenvalue comparison of healthy and faulted machines is presented. This analysis is verified by transient simulations of the dynamic phasor model and experiments. The eigenvalue analysis and the results of experiments and simulations show that the effect of stator inter-turn fault in transients of positive and negative sequence currents is very small. Also the stator inter-turn fault produces coupling between transients of positive and negative sequence currents.