Fault severity estimation using nonlinear Kalman filter for induction motors under inter-turn fault

Fault severity estimation is an important part in condition-based maintenance, by which a right time and suitable maintenance policy can be planned. For stator winding inter-turn short circuit fault, its severity is represented by two parameters, percentage of shorted turns and fault loop resistance. Research on severity estimation of this fault has been focused on late stage of the fault development process, when the estimation of only one parameter, percentage of shorted turns, is required. As an attempt to overcome this, this paper proposes a method to estimate both parameters employing nonlinear Kalman filter using an equality constraint on them. The constraint is derived from a sequence component model analysis. The estimation of both fault parameters helps track the degradation process from its incipient stage.