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A panel Switchboard.

This board consists of two three-phase generator panels and two-line panels, the former occupying the left, and the latter the right side of the structure. Fig. 76 shows clearly the location of the various devices at the back of

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the board, including the bus bars for connecting the generators with the line panels. The main switches are arranged so that only the handle is on the front of the board, the other parts being behind it. Each panel is provided with three ammeters, and two voltmeters are mounted upon a swinging bracket at the left. This ar

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Series alternating Switchboards.

rangement of voltmeters is quite common, specially with long boards. The line panels are provided with three fuses each, located at the bottom. The sockets seen at the bottom of the generator panels are for the purpose of controlling the exciter circuits. The small sockets, just below the rheostat wheels, are for connecting the voltmeter between any pair of lines. To the right of the first generator panel is seen a ground detector switch by means of which this instrument is connected with the circuits.

Switchboards for series alternating current

arc lighting Arc lights are operated in series by alternating currents derived from transformers provided with mechanical means to maintain the current constant. The switchboards used for this service are constructed upon the same general principle as those used with continuous currents, but, as a rule, each board is arranged to control one circuit only, although there is no difficulty in arranging the lighting and the transformer circuits so that they may be interchanged if desired. The differences between the regular arc switchboards and those used for alternating current service are simply those required on account of the difference in the nature of the currents.

The front and back, respectively, of an alternating current arc switchboard for a 35-light circuit are shown in Figs. 77 and 78. The plugs and sockets are substantially the same as those shown in Figs. 53 and 54. The only devices shown on this board that are not used on continuous current boards are two transformers, one of which


Figures 77-78. Front and back of alternating current arc light switch boards.

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