Determination of shaft position from shaft voltage on a synchronous generator

Abstract

Shaft voltages and currents are an unavoidable characteristic of rotating machines. Recently there has been renewed interest in the diagnostic possibilities of these signals. This paper presents a technique to determine the mechanical shaft position using a capture of the shaft voltage and a mechanically aligned prerecorded reference. The tests were carried out on a 400 V salient 4-pole generator with rotating exciter. Gold-bristle brushes were used which provided excellent signal clarity. A PC based acquisition system was used which facilitated averaging to further reduce noise as well as the capture ofabsolute position using a rotary encoder. The technique successfully determined the shaft position using a test signal which was considerably distorted. This technique could prove useful in the location offaults within a machine, and investigation is continuing.

Impact of stator interturn short circuit fault on shaft voltage in a synchronous generator

“…The shaft voltage is induced in the shaft of the synchronous generator due to the asymmetry load distribution, the rotor eccentricity, the rotor/ stator interturn short circuit etc. The shaft voltage reduces the mechanical strength of the shaft and damages the bearings [1][2][3]. Therefore, it is significant to comprehensively study the inherent characteristics of the shaft voltage under the typical running conditions in order to fully monitor and control the shaft voltage.…”

Multiple fault diagnosis on a synchronous 2 pole generator using shaft and flux probe signals

“…In order to limit these negative effects, shaft grounding brushes are usually employed to attenuate the circulating currents [3]. Although shaft signals are practically unavoidable and are caused by a number of reasons including magnetic asymmetries due to manufacturing imperfections, it has been found to be quite valuable in the area of condition monitoring [2,4].…”