Hawkins Electrical Guide v. 07 (of 10) / Questions, Answers, & Illustrations, A progressive course of study for engineers, electricians, students and those desiring to acquire a working knowledge of electricity and its applications

by N. Hawkins

Ans. No. The resultant is obtained by simply multiplying one of the pressures by 1.41.

This is evident from fig. 2,130. Here the two pressures OA and OB are equal as indicated by the dotted arc. Since they act at right angles, OB is drawn at 90° to OA. According to the equation of the right angle triangle, the resultant AB = √(1² + 1²) = √2 = 1.4142 which ordinarily is taken as 1.41.

This value will always represent the ratio between the magnitude of the resultant and the two component forces, when the latter are equal, and have a phase difference of 90 degrees.

Forms of Circuit.—Alternating current systems of distribution may be classed, with respect to the kind of circuit used, in a manner similar to direct current systems, that is, they may be called series, parallel, series parallel, or parallel series systems, as shown in figs. 2,131 to 2,134.

Fig. 2,130.—Diagram for obtaining the resultant of two equal component pressures acting at right angles.

Series Circuits.—These are used in arc lighting, and series incandescent lighting, a constant current being maintained; also for constant current motors and generators supplying secondary circuits.

Figs. 2,131 to 2,134.—Various forms of circuit. These well known forms of circuit are used in both alternating and direct current systems. The simple series circuit, fig. 2,131, is suitable for constant current arc lighting. Fig. 2,132, shows the parallel constant pressure circuit; this form of circuit is largely used but is seldom connected direct to the alternator terminals, but to a step down transformer, on account of the low pressure generally required. Fig. 2,133 illustrates a parallel series circuit, and 2,134, a series parallel circuit.

Several forms of constant current alternator, analogous to the Thompson-Houston and Brush series arc dynamos, have been introduced. In the design of such alternators self-induction and armature reaction are purposely exaggerated; so that the current does not increase very much, even when the machine is short circuited. With this provision, no regulating device is required.