It is the object of this paper to describe a new method for the close determination of the field exciting current of three phase salient pole type synchronous machines at any specified p. f. and to make its use directly in the case of their design. Since the machine of this type have been developed several decades have passed and numerous papers have been appeared on the subject, but very little is convenient for the predetermination of field
m. m. f. especialy at low p. f. load. It is also shown that the voltage regulation at any p. f. can easily be obtained from the exciting mmf so determined, with the combined use of the well known no load saturation curve. Principal feature in this paper is based on the experimental data that the mmf v_??_ctor of the loaded armature reaction describes an elliptical locus when its p. f. is varied and the load kept as constant. Chief methods hithetro published will probably be those adopted in the Standard of A. I. E. E. and that of the Blondel's so-called two reaction method. In Section I, brief descriptions are given on these methods just mentioned, classifying as
m. m. f. vector and
e. m. f. vector, and showing that these are all to put into circle diagrams. Besides it is shown that the decomposition of the armature reaction into two components, corresponding to unity p. f. and the other to zero p. f., has some values in design, but one it is too complicated for rapid practical application, and not so adeqate in testing the voltage regulation. In section II, there is described the advantage of the new elliptic
m. m. f. method proposed by the writer over any other ordinary methods in its simplicity and in its close agreement with the actual test results. It is pointed out there that the transformaiion coefficient of the armature reaction into field
m. m. f. frequently refered by some continental writers is not so strict. Finally, some results of actual tests together with those obtained from the proposed method are shortly given to show its degree of precition.
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