Diagnosis of a stator winding short-circuit fault on induction machines running in variable speed conditions

The aim of this paper is to contribute to the electrical machine diagnosis running as adjustable speed drive. The analyzed signal is the leakage flux flowing around the machine, which is considered to be an image of the airgap flux density. An analytical expression of the airgap flux density is presented and gives sensitive spectral lines to a stator winding short-circuit fault in an induction machine. The study is done on a frequency range up to few kilohertz, around the slotting spectral lines. The originality of this paper is that the study is focused on machines fed by the mean of a converter. The theory is verified by experimental tests and the results show what precautions are necessary to take in order to obtain spectra which can be used for diagnosis.