Simplified axial flux spectrum method to detect incipient stator inter-turn short-circuits in induction machine

The aim of this paper is to develop a tool for condition monitoring of squirrel-cage three-phase induction machines using axial flux measurement. The emf induced in a search coil which is proportional to the axial flux derivative, is measured in order to detect, in presence of voltage source dissymmetry, incipient stator inter-turn short-circuits in working induction machines. Starting from a theoretical analysis of the axial leakage flux spectrum associated to this fault, the measurement of the corresponding emf in the search coil is examined. The proposed simplified axial flux spectrum gives directly the sensitive frequency components to study faults for both no-load and rated-load operations. This spectrum enables us to observe directly the evolution of these components during the fault conditions, materialized by the presence of a few stator inter-turn short-circuits, compared to normal operation. An experimental test-bed with a 230 V/400 V-50 Hz-11 kW three-phase squirrel-cage induction machine has been used to verify the efficiency of this tool. Finally, the performance of the proposed technique is proved experimentally.