A new method for synchronous generator core quality evaluation

A technique for detecting the presence and severity of inter-laminar short circuits and estimating the status of core compression (or looseness) in synchronous generators (or large motors) with single test equipment is proposed in this paper. The core loss measurement obtained from a flux injection probe that injects flux into adjacent teeth over a localized region, is used as an indicator for detecting and distinguishing the two fault conditions. An injection probe system was developed and tested, in the laboratory using stacks of full size generator laminations with various induced fault conditions. The probe was shown to detect the presence of as few as 5 shorted laminations, and to approximately gage the degree of core compression (looseness). A unique differential probe was developed and tested to demonstrate the potential to detect two shorted laminations.