State of the Art on Stray Flux Analysis in Faulted Electrical Machines

The aim of this paper is to present an overview of the stray flux analysis to detect faults in electrical machines. The investigation is dedicated to AC electrical machines in particular induction and synchronous machines which are the most used motors and generators in industry. The stray flux is sensed outside the machine case with simple non-invasive sensors. It can be used to detect broken bars, rings and dampers in AC electrical machines. It can also detect early stage short-circuits in both stator and rotor windings. A large range of mechanical faults can be detected by analyzing the stray flux. Finally, any kind of unbalance whatever the location can be detected by stray flux sensors.