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 pre-recorded 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 of absolute 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 of faults within a machine, and investigation is continuing.