Vectors and vector diagrams; applied to the alternating current circuit, with examples of their use in the theory of transformers, and of single and polyphase motors, etc

by William Cramp

This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1909 ...come out 3018, or about 0-06 per cent. low. This is, of course, less than the error of a very good voltmeter, so that neglect of this factor is usually justifiable, and the transformer equations are very considerably simplified; for equation (86) becomes which is very easy to work out, and quite near enough for most practical purposes. Current Calculation.--The total primary current in the transformer is Cs we already have as § amperes; Go we also have in the form That is, we have Co in terms of Ei as axis of reference. Now, in order to add directly Co and Cs we must have both Co and Cs referred to one axis. We chose Cs as the axis of reference and wrote it = §'. As Co in the form given above is in terms of Ei as axis of reference, it cannot be added directly to C,. But it has already been shown that which is very near the value given above, showing that Ei and Cs are nearly in phase. We get now The tangent of the angle of lag of Ci behind Cs And it has already been shown that the applied voltage leads C, by 30 minutes, or /. Hence the applied voltage leads the total primary current Ci by 0 = J0 + 6 = 6J So that the power factor = cos 0 = 0-99. Example.--Transformer worked at constant applied Pressure.--The case just considered is a very simple one, which on the one hand does not often occur in practice, and on the other does not exemplify the use of the change of axis of reference or the case of inductive secondary load. We will therefore work out the behaviour of this same transformer under the following the primary current and the secondary pressure at no load and at a load of 30 amps. with a power factor of 0-5 and a constant applied primary pressure of 3000 volts. No Load.--Now at no load C2 = C« = 0 and Z becomes infin...

58 pages, Paperback

Published January 1, 2012