Current monitoring for detecting inter-turn short circuits in induction motors

In this paper the stator winding itself is used as the sensor for the detection of abnormalities in the stator winding. To achieve this task, detailed analysis of the air gap flux distribution and its dependence on the particular machine configuration is carried out. The analysis presented is based on the rotating wave approach which accounts for all the stator and rotor MMF harmonics, stator and rotor slot harmonics and harmonics due to saturation. It is shown that the most reliable indicators of the presence of the fault are the lower sideband of field rotational frequency with respect to the fundamental, together with some of the components that are related to slotting. Some of them increase as functions of the link current, in a range from 0 to over 10% and some components decrease in the range 0-12%.