Motion Picture Operation, Stage Electrics and Illusions

Table VIII. — Size of Wires for Motors of Different Horse Power

DIRECT CURRENT
		110 Volts			220 Volts
H. P.		Full- load Current	Size of Wire Mains	Size of Wire Branches	Full- load Current	Size of Wire Mains	Size of Wire Branches
1		8	14	14	4	14	14
2		15	14	12	8	14	14
3		23	10	8	12	14	14
4		30	8	6	15	14	12
5		38	6	6	19	12	10
7	.5	56	5	4	28	8	8
10		75	3	1	38	6	6
SINGLE-PHASE
1		12	...	12	6	...	14
2		23	...	8	11	...	12
3		33	...	6	16	...	10
4		44	...	4	22	...	8
5		53	...	3	26	...	6
THREE-PHASE
1		...	...	...	3	14	14
2		...	...	...	5	14	14
3		...	...	...	8	14	14
4		...	...	...	10	14	14
5		...	...	...	13	14	12
7	.5	...	...	...	19	12	8
10		...	...	...	26	8	6

Music Stands

Music Stands.—Music stands are used by the musicians and are generally placed between the first row of seats and the stage. Each musician should be provided with an individual stand, although if necessary, two or three can get along with one stand.

No first-class theater should be fitted up with less than twenty outlets for musicians’ lights. In the Metropolitan Opera House of New York there are one hundred. Houses used exclusively for vaudeville do not, however, need that many. In houses devoted to grand opera, often as many as one hundred or more musicians are employed at the same time. To take care of such a number, the music stands should be wired with pin-plug connectors so that connections may be made from one to the other. Long flexible connections are necessary for most music stands.

Sometimes it is necessary to crowd the orchestra under the stage and at other times, with musical comedies, for instance, they must be brought out where they can see the movements of the actors.

The more the circuits are subdivided, and the different lights made independent of each other, the better it will be and the less the annoyance in case a fuse blows. The fuses should always be arranged at the switchboard so that it will not be necessary for the electrician to work in front of the audience in cases of trouble. For this reason extra stands should also be kept on hand.

A main switch controlling the lights should be placed where one of the musicians can handle it. In dark scenes these lights must often be turned out. If these lights are left under the control of the stage electrician they will be more likely to be forgotten at the critical moment than if under the control of the men who need them.

An eight candle-power lamp for each stand will be sufficient and this is usually placed inside a special reflector which allows the light to fall upon the music sheet only. Stage cable of good quality should be used for the connections; there is too much rough handling for reinforced cord. The use of the ordinary attachment plug should be avoided; use approved pin-plug connectors.

Open Work

Open Work.—Open work is not allowed in theaters.

Operating Room

Operating Room.—See special chapter on “Operating Room.”

Panel Boards

Panel Boards.—Panel boards are really small switchboards, the switches and cut-outs being mounted usually upon slate. The slate must be free of metal seams; these, if present, often manifest themselves by heating. Panel boards, unless located in the immediate vicinity of the main switchboard, and where they are enclosed in a compartment, must always be placed in standard metal cabinets.

National Electrical Code Rules for Panel Boards

The following specifications are intended to apply to all panel and distributing boards used for the control of light and power circuits, but not to such switchboards in central stations, sub-stations, or isolated plants as directly control energy derived from generators or transforming devices.

Design

The specifications for construction of switches and cut-outs given in the following pages must be followed as far as they apply.

In the relative arrangement of fuses and switches, the fuses may be placed between the bus-bars and the switches, or between the switches and the circuits, except in the case of service switches. When the branch switches are between the fuses and the bus-bars, the connections must be so arranged that the blades will be dead when the switches are open.

When there are exposed live-metal parts on the back of a board, a space of at least one-half inch must be provided between such live metal parts and the cabinet in which the board is mounted.

Spacings

Table IX.
THE MINIMUM DISTANCE THAT MUST BE MAINTAINED
BETWEEN BARE LIVE METAL PARTS (BUS-BARS, ETC.)

	Between Parts of Opposite Polarity, Except at Switches and Link Fuses				Between Parts of Same Polarity at Link Fuses
	When Mounted on the Same Surface		When Held Free in Air
Not over 125 volts		3⁄4 inch		1⁄2 inch		1⁄2 inch
Not over 250 volts	1	1⁄4 inch		3⁄4 inch		3⁄4 inch
Not over 600 volts	2	3⁄4 inch	1	3⁄4 inch

At switches or enclosed fuses, parts of the same polarity may be placed as close together as convenience in handling will allow. It should be noted that the above distances are the minimum allowable, and it is urged that greater distances be adopted wherever the conditions will permit.

The spacings given in the first column apply to the branch conductors where enclosed fuses are used. Where link fuses or knife switches are used, the spacings must be at least as great as those given in the following section on fuse spacing. The spacings given in the second column above apply to the distance between the raised main bars and between these bars and the branch bars over which they pass. The spacings given in the third column are intended to prevent the melting of a link fuse by the blowing of an adjacent fuse of the same polarity.

Panel boards of special design, in which the insulation and separation between the bus-bars, and between the other current-carrying parts is secured by means of barriers or insulating materials instead of by the spacings given above, must be submitted for special examination and approved before being used.

Fuse Spacings

Spacings must be at least as great as those given in Table X, which applies only to plain, open link fuses. The spaces given are correct for fuse blocks to be used on direct-current systems, and can therefore be safely followed in devices designed for alternating currents. If the copper fuse tips overhang the edges of the fuse block terminals, the spacings should be measured between the nearest edges of the tips.

A space must be maintained between fuse terminals of the same polarity of at least one-half of an inch for voltages up to 125 and of at least three-quarters of an inch for voltages from 125 to 250. This is the minimum distance allowable, and greater separation should be provided when practicable.

For 250 volts, boards, or blocks with the ordinary front-connected terminals, except where these have a mass of compact form equivalent to the back-connected terminals usually found in switchboard work, a substantial barrier of insulating material, not less than one-eighth of an inch in thickness, must be placed in the “break” gap—this barrier to extend out from the base at least one-eighth of an inch farther than any bare live part of the fuse-block terminal, including binding screws, nuts and the like.

For three-wire systems cut-outs must have the break-distance required for circuits of the potential of the outside wires.