TYPES AND SIZES OF TUNGSTEN LAMPS NOW MADE
There are about two hundred different types and sizes of tungsten filament lamps now standard for various kinds of lighting service. For 110-volt service, lamps are made in sizes from 10 to 1000 watts. Of the smaller sizes, some are made in round and tubular-shaped bulbs for ornamental lighting. In addition there are the candelabra lamps used in ornamental fixtures. Twenty-five- to five hundred-watt lamps are made with bulbs of special blue glass to cut out the excess of red and yellow rays and thus produce a light approximating daylight.
For 220-volt service lamps are made in sizes of from 25 to 1000 watts. For sign lighting service, 5-watt lamps of low voltage are made for use on a transformer located near the sign to reduce the 110 volts alternating current to that required by the lamps. Lamps are made from 5 to 100 watts for 30-volt service, such as is found in train lighting and in gas engine driven dynamo sets used in rural homes beyond the reach of central station systems. Concentrated filament lamps are made for stereopticon and motion picture projection, floodlighting, etc., in sizes from 100 to 1000 watts, for street railway headlights in sizes below 100 watts and for locomotive headlights in sizes from 100 to 250 watts. For series circuits, used in street lighting, lamps are made from 60 to 2500 candlepower. Miniature lamps cover those for flashlight, automobile, Christmas-tree, surgical and dental services, etc. They range, depending on the service, from ½ to 21 candlepower, and in voltage from 2½ to 24.
Standard Tungsten Lamps, 1923.
This illustrates some of the two hundred different lamps regularly made.
STANDARD VOLTAGES
Mention has been made of 110-volt service, 220-volt service, etc. In the days of the carbon incandescent lamp it was impossible to manufacture all lamps for an exact predetermined voltage. The popular voltage was 110, so lighting companies were requested in a number of instances to adjust their service to some voltage other than 110. They were thus able to utilize the odd voltage lamps manufactured, and this produced a demand for lamps of various voltages from 100 to 130. Arc lamps had a resistance (reactance on alternating current) that was adjustable for voltages between 100 and 130.
Similarly a demand was created for lamps of individual voltages of from 200 to 260. The 200- to 260-volt range has simmered down to 220, 230, 240 and 250 volts. These lamps are not as efficient as the 110-volt type and their demand is considerably less, as the 110-volt class of service for lighting is, with the exception of England, almost universal. Thus 110-volt service means 100 to 130 volts in contra-distinction to 200 to 260 volts, etc. The drawn tungsten wire filament made it possible to accurately predetermine the voltage of the lamp, so now that the carbon incandescent lamp is a thing of the past, there is no need for so many different voltages. Several years ago standard voltages of 110, 115 and 120 were recommended for adoption by all the electrical societies in the United States, and practically all central stations have now changed their service to one of these voltages.