End-Ring Wear in Deep-Well Submersible Motor Pumps

Wear of end ring is to date an unreported and uninvestigated failure that very frequently takes place in deep-well submersible motor pumps. This article first analyses the particularities of these induction motors, especially their unusual rotor manufacturing process. Failure mechanism related to the end-ring wear is described, showing several examples of damaged rotors in a motor repair shop. Then, the difficulties of its diagnosis through conventional rotor asymmetry indicators are described, caused by the subtlety of this fault and the very easy appearance of false negatives. The end-ring wear detection through a multicomponent approach is researched through simulation, laboratory results, and the diagnosis of two-field motors showing that new fault alarm levels need to be defined. To perform this last step and for the first time in the technical literature, two induction motors working in a deep borehole have been continuously monitored (one measure every six operating hours) for almost one year.