Power Transients in A-C. Motors A Watt-Oscillograph Study

The purpose of this paper is to describe the application of the watt-oscillograph to the study of the performance of rotating a-c. machinery under transient conditions. Some typical transient cases are presented with a view to illustrating the possibilities of such an application. The analysis of a film taken with the watt-oscillograph yields not only power, but also current and power factor. It is thus possible, for the case of sinusoidal voltages and currents, to determine the locus of the current vector as it changes from one position to another. The paper also describes the watt elements of the oscillograph developed for this study, with data as to the degree of accuracy that may be expected from them. An outline of the method of analyzing an oscillogram so as to obtain the performance curves and the current locus is also given.