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Page 411 | Volume 2 | Chapter 25 | Auxiliary Apparatus

Ques. How is this remedied to some extent?

Ans. The contact pieces are so shaped that they open along their whole length at the same time, so as to prevent the concentration of the arc at the last point of contact. This feature is clearly shown in fig. 461.

Fig. 463. - A quick break knife switch of the single throw, single break, one pole type.
Fig. 463.—A "quick break" knife switch of the single throw, single break, one pole type. The contact blade is held between the jaws by their clamping friction until the handle compresses the spring sufficiently to force the blade out. As soon as it breaks contact with the Jaws, the spring expands and drives the blade away from the jaws with greater rapidity than could be done by hand. The object of this action is to break the arc as quickly as possible to prevent burning the metal of the switch.
Figs. 464 and 465. - Snap switch; views showing switch with cover on, and exposed to show mechanism.
Figs. 464 and 465.—Snap switch; views showing switch with cover on, and exposed to show mechanism. The switch is provided with indicating dial which registers "on" and "off" positions.

Fig. 466.—Gas Engine snap switch. The first snap makes connection so that igniter is run from storage battery; second snap connections are changed so that igniter is supplied from dynamo; third snap makes connections so that dynamo supplies igniter and charges storage battery; fourth snap, all off.

Ques. For what service are "snap" switches suitable?

Ans. They are used on circuits containing lamps in comparative1y small groups, and other light duty service.




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