Abstract
As a diagnostic method of cage rotor in an induction motor, the stator current monitoring or the air gap flux monitoring has been developed. However, the air gap monitoring method can not be applied to every case because it is necessary to install a search coil on the stator.
In this paper, as a simpler diagnostic method, we studied on the leakage flux monitoring method. In this method, any pre-installation of a search coil to motor is not needed and the cage rotor can be diagnosed by the leakage flux waveforms and the feature frequency components of its spectra.
First, the space distributions of leakage flux are clarified by the analyzed and measured results. Next, we present the feature harmonics detector which rejects the normal harmonic components of leakage flux and confirm the effectiveness of this detector. Finally, the measured results obtained by the motor with artificial faults such as broken bars, demonstrate the availability of those analytical results and this method. As the results, it became possible to estimate quantitatively the leakage flux magnitude in the case of rotor faults and to prognosticate the cage rotor faults.
