Generator rotor angle measurement by stroboscopic means

The stroboscopic equipment described in the paper was originally designed and used for observation of machine rotor angles under conditions where recording was not required. Further development of the apparatus, together with the establishment of a ciné-film recording technique, extended its use to the recording of rapid rotor-angle changes. The general principle of the observation of rotating machinery by stroboscopic methods is, of course, well known. In this application, the flashing light source is triggered once per cycle by a voltage obtained from a voltage transformer. The particular voltage transformer chosen will depend upon the primary voltage with which it is desired to compare the machine rotor movement. A ciné camera driven at 50 frames/sec is used to obtain a ciné-film recording of the stroboscopic image. This permanent pictorial record of the rotor movement during the period of observation may be projected on to a screen in the usual way, or an angle/time curve may be drawn from an inspection of the film. The particular value of this method lies in the accuracy with which very rapid changes of rotor angle are recorded. It suffers from a disadvantage, since viewing of results is delayed until the film has been developed. The apparatus has been found most helpful in a number of transient tests on turbo-generators.