Calculation of Sudden Short-Circuit Phenomena of Alternators

The theory and explanation of the electromagnetic phenomena involved in the sudden sbort circuit of alternators, as given by Berg and Boucherot, is first briefly considered. It is shown how complex the different resistances and reactances are that enter the equations of sudden short circuits. New methods are developed for the experimental determination of these quantities by simply determining the rise of direct current in the field and armature circuits. (See II) Also new simple methods are given, based on theoretical equations, for the calculation of short circuits directly from oscillographic records. (See IV). Data relating to the short circuit of a 45-kv-a. alternator are given; also an electrical device, designed by the writer and used in most of the tests, for short-circuiting a machine at any given point of the e.m.f. wave, is described. (See III). As a whole, an attempt is made throughout the paper to put calculations of sudden short circuits on a sound rational basis and to test the correctness of the theories given. The paper is divided into the following self-explanatory sections: I-General theory and explat4ation of the electromagnetic phenomena of sudden short circuits of alternators. II-Experimental methods for the determination of alternator constants. III-Sudden short-circuit tests. Three-phase, single-phase, etc. IV-Methods of calculation. V-Determination of armature reactance (impedance). VI-Effect on supply. VII-Critical résumé and some conclusions. VIII-Discription of apparatus and list of symbols.