Identifier: cyclopediaofappl04amer (find matches)
Title: Cyclopedia of applied electricity : a general reference work on direct-current generators and motors, storage batteries, electrochemistry, welding, electric wiring, meters, electric lighting, electric railways, power stations, switchboards, power transmission, alternating-current machinery, telegraphy, etc.
Year: 1916 (1910s)
Authors: American Technical Society
Subjects: Electric engineering
Publisher: Chicago : American Technical Society
Contributing Library: Northeastern University, Snell Library
Digitizing Sponsor: Northeastern University, Snell Library

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to deliveralternating current at 90 or 110volts; P and S are the primaryand secondary coils of an ordinarytransformer. The primary P isconnected to A and B as shown.Fig. 218. Connections for Auto step-up The secoudary S has onc-tcnth as Transformer many turns as P, therefore, thevoltage induced in S is one-tenth of the voltage acting on P, or 10volts. Let the dotted arrows represent the directions of the inducedelectromotive forces in the two coils at a given instant. Then thelong heavy arrow will represent the direction of the voltage betweenthe mains at the same instant, inasmuch as the induced voltage inthe primary coil of a transformer is always opposed to the supplyvoltage. Auto Step-Up Transformation. The 10 volts induced in thecoils, Fig. 218, will help push current into the service mains if weconnect from supply main A, out of which the current at the giveninstant is tending to flow, to terminal g of coil S; connect from 266 ^ 1 1 1^ ^ •=* I§s 1 l<P sS • B S ^■■ D
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<Pi oo ei o p< Q H < ^ !r5 o^Q O<!< V as -S ai<; w o -« w ^ w -^^ «« o rt§ ?.w SO ■s < OW O o t) w O ZOH ALTERNATING-CURRENT MACHINERY 253 terminal / to service main C; and connect from service main D tosupply main B, as shown by the dotted lines. In this case, the vol-tage induced in the coil S is added to the supply voltage, and theservice voltage is, therefore, 110 volts. Auto Step-Down Transformation. The 10 volts induced in thecoil S will oppose the flow of current into the service mains ifwe connect from supply main A to terminal /, connect from terminalg to service main C, and connect from service main D to supplymain B, as shown by the dotted lines in Fig. 219. In this case theinduced voltage in the coil S is subtracted from the supply voltage,and the service voltage is now 90. Current Relations. In Figs. 218 and 219 the directions of theinduced voltages in P and S are shown by the dotted arrows. Theseinduced voltages are in the same direction in the

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