Vector Diagrams of Polyphase Synchronous Machinery

The paper is concerned with the theory and application of a vector diagram for synchronous machines which is expressible in terms of coefficients that are easy to measure if a source of large wattless currents is available. This vector diagram is compared with the diagrams in general use, and some reasons are advanced, in regard to the latter, for the discrepancies between predicted and observed results which may occur when they are applied. The theory of the diagram and the tests necessary for the definition of its coefficients are considered for the cases of a salient-pole and barrel-rotor machine on infinite busbars and on bars of varying voltage, and it is shown that, in general, good agreement is obtained between the predicted and observed results for regulation and load-angle shift. In the Appendix a brief outline of the mathematical theory is provided.