EFFECTS OF ECCENTRICITIES ON SHAFT SIGNALS STUDIED THROUGH WINDINGLESS ROTORS

Shaft signals of electric rotating machines offer potentials for defec t detections. The signals are affected by many factors. This study spe cifically focuses on how eccentricities affect shaft signals through t heoretical predictions and tests conducted on windingless rotors. Wind ingless rotors imply currentless rotors. For symmetrical synchronous m achines running at steady synchronous speeds, the induced rotor curren ts are zero while harmonics are neglected. One advantage in experiment s for this study is that air gaps can be shimmed accurately at standst ill without end brackets; certain tests can be conducted at standstill without facing unmanageable locked-rotor currents for the test machin es. Shaft signals decrease when the rotor of a machine closely situate s at the center of stator bore. Shaft signals increase under greater e ccentricities when stator and rotor axes are parallel. Tilted rotors r educe shaft signals. Even when there are no rotor windings, inherent p ositional characteristic exists. This characteristic produces cyclic s haft-signal components that are related to rotor revolutions.