Alternating Current Engineering, Practically Treated (Paperback)

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. 1904 Excerpt: ...is short-circuited through the ammeter, and since the impedance of the ammeter is negligible, the drop through the series transformer is negligible. Series transformers are often used in compounding alternators when it is desired to get an increasing voltage from the secondary of the transformer with increasing current output from the alternator, the main alternator current passing through the primary of the series transformer. THE COMPENSATOR. There is another type of transformer in use, called the compensator, where the secondary winding, instead of being separate from the primary, is a continuation of it. The advantage of such an arrangement is that, for the same energy to be transmitted, the compensator is smaller than the transformer. The disadvantage is that the secondary is electrically connected to the primary, and thus the compensator is not suited for use on high potential circuits. Owing to the reduction in its size as compared with a transformer, and the consequent reduction in its cost, a compensator is most desirable on low potential circuits, in which the secondary voltage is not small as compared with the primary. It is, therefore, usually used for starting induction and synchronous motors. The principle of the action of a compensator can best be explained by reference to Fig. 55. Assume the primary voltage to be 100, and the secondary to be 50, as shown in the figure. The ratio of turns, primary to secondary, in the compensator will, therefore, be just as in a transformer, 100 to 50. The excitation current flows from A to B. The current in the secondary circuit, C, is, however, the sum of the current from B to D and from A to D. Thus, if the external current in the secondary is 10, 5 amperes will be supplied by the secondary winding, and 5 ...