Introduction of the Zero-Sequence Stray Flux as a Reliable Diagnostic Method of Rotor Electrical Faults in Induction Motors

Lately, the zero-sequence current has been proposed for reliable detection of faults in induction motors. The zero-sequence current offers some distinct advantages compared to traditional methods, one of which is that it is able to detect a variety of faults with a single analysis. Despite its numerous advantages, the zero-sequence current has one significant drawback; it can only be applied to delta-connected induction motors or star-connected with the stator neutral connected to the supply. However, in many industrial cases, the large induction motors are connected in star without the neutral connected, to avoid extra losses. In those cases, the zero-sequence current method cannot be applied as the zero-sequence current simply does not exist. To overcome this drawback, this paper proposes for the first time the use of the zero-sequence stray flux for the detection of induction motor rotor electrical faults. It will be shown that the zero-sequence flux carries all the advantages of the zero-sequence current, while it can be applied to any 3-phase electrical machine independently from the stator winding configuration.