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1933 - street and highway lighting development a decided advance in efficiency

SODIUM-VAPOR STREET AND HIGHWAY LIGHTING

CD 1966002 E&MP27.084

Electric Lighting

June 14, 1933

The sodium lamp is a product of many years of organized research for a utilitarian light source more efficientthan the MAZDA incandescent lamp. Its successful use for street and highway lighting shows that this development offers a possibility of a decided advance in efficiency and utility in this field.

The 10,000-lumen lamp was developed to effect a substantial improvement in highway lighting over the incandescent units, with the expectation that ultimately this benefit would be obtained at less cost than that involved in obtaining similar results with other lighting systems. It was believed that in the meantime sodium-vapor lighting would be particularly advantageous for demonstration installations sponsored by those seeking to arouse public interest in more and better highway lighting. Thus, while the lamp and the highway luminaire designed especially for it, are at present too expensive to warrant their widespread substitution for MAZDA lighting where cost is the major consideration, the state of simplification and production already reached provides for reasonable cost for demonstration units and installations.

The special advantages of sodium-vapor lighting for streets and highways are:

1. High efficiency. For about the same amount of power that is used by a 4000-lumen series incandescent street lamp, this sodium-vapor lamp generates 10,000 lumens.
2. Greater visual acuity. At normal interior intensities, the monochromatic light (practically all orange-yellow) permits easier discernment of detail than do corresponding intensities of "white" light. Tests now being conducted may show this to be an aid to visibility on streets and highways. The color is in the range to which the eye is most responsive.
3. No glare. Because the glow comes from a large tube - and from the entire tube - the light source appears to be much less brilliant; objectionable glare is eliminated.
4. A soft, agreeable color. The golden-orange light is pleasing and restful; it is sufficiently unusual and distinctive to attract much favorable attention to a demonstration installation, and is of practical value also for the marking of traffic routes or intersections.
5. Easy to install and operate. Lamp and luminaire are designed for conventional a-c. series and multiple lighting circuits, with a minimum of circuit and operating complications.
6. Reasonable cost. Long lamp life, high efficiency, further simplification, and increased production are expected to bring about in the relatively near future a lower cost of sodium-vapor lighting that will make it an economical means to greater safety, comfort, and convenience for night traffic.

Ten-thousand lumen a-c. sodium-vapor lighting was first installed at Revere, Mass., in January, 1934, when eleven luminaires were used to light an under-pass highway intersection.* This was followed closely by the installation of ten luminaires on the Boston-Worcester Turnpike at Newton, Mass.; eight luminaires on the Hartford-Meriden Road at Wallingford, Conn.; and the revamping of the Balltown Road experimental installation near Schenectady, N.Y. As this is written, other installations at New York City; Syracuse, N.Y.; Pittsburgh, Pa.; Rochester, Minn.; and Three Rivers, Quebec, Canada, are being constructed. These are sponsored by central station companies and public authorities, to demonstrate the value of highway lighting and the practicability of the sodium-vapor lamp.

The G-E 10,000-lumen Sodium-vapor Lamp
This lamp consists of a long, evacuated bulb of special glass, enclosing at each end a coiled filament (cathode) surrounded by an open-ended box of molybdenum (anode). Each anode is connected to one side of the filament, the conductors passing through a seal at one end of the bulb and connecting to a four-pin molded-composition tube base. A small quantity of pure metallic sodium, and neon at low gas pressure (for starting) are included in the bulb.

The lamp is about 16 inches long, exclusive of the pins on the base, and about three inches in diameter.

To operate the lamp, each cathode is supplied with 10 amperes at approximately 2 volts. After a short preheating interval, the arc potential is applied across the anodes. The lamp then glows brilliantly with the characteristic red neon color. As heat is accumulated, the discharge gradually acquires the orange-yellow color of the sodium-vapor arc. The maximum output is reached in about 30 minutes, but acceptable lighting conditions are usually obtained within 10 or 15 minutes. Since the lamp will not cool completely during short power interruptions, the time of recovery from such an interruption is usually short.

The rated are current is 6.6 amperes, requiring a potential of about 28 volts.

The light is derived from electronic displacement in the sodium vapor. The entire bulb is luminous, with a brilliancy much less than that of an incandescent filament. The normal operating temperature is about 480 deg. F., which is obtained by conserving heat with an enclosing vacuum flask.

The expected useful life of the lamp is at least 1350 hours. Neither life nor light output are greatly affected by normal changes of current or surrounding temperature.

The power consumption of the lamp itself is about 200 watts, with a power-factor of 0.9 resulting from the voltage wave-form. The luminous efficiency of the lamp is, therefore, about 50 lumens per watt. The over-all efficiency is reduced to about 40 lumens per watt because of the auxiliary equipment required. This figure may be compared with 15 to 19 lumens per watt obtained from incandescent street lamps.

Vacuum Flask
Although it is made separate form the lamp for the sake of economy, the enclosing flask is essential to the lamp in order to obtain the desired temperature and vapor pressure. It consists of a double-walled, evacuated, heat-resistant glass jar approximately 16 inches long and four inches in outside diameter. Asbestos washers seal the open end.

Novalux Sodium-vapor Luminaire
This novel and unusual luminaire consists of both parabolic and plane reflecting surfaces, carefully designed to suit the characteristics of the lamp. They are made of electro-chemically processed aluminum, which has a coefficient of reflection of more than 80 per cent. The finish is durable and is easily cleaned.

The characteristic unsymmetrical light distribution desirable for highway-lighting service is provided by this unit.

A housing on the curb side contains, for series-circuit operation, two auto-transformers for cathode heating, a timer for cathode preheating, a film-cutout holder, lamp and flask holders, a lamp socket, and a radio-interference suppresser. For multiple-circuit operation, a special transformer and fused cutout replace the auto-transformers and film-cutout holder.

The lamp and flask are supported by simple holders in a horizontal position without strain on the socket or leads. They are easily inserted or removed through a door in the back of the housing.

Insulation from the high voltage of a series circuit, and adaptation to line currents of other that 6.6 amperes are provided, where required, by a Novalux Type IL transformer of standard construction. This equipment can be applied to new or existing a-c. lighting circuits in the conventional manner.

Other Lamps
A General Electric 6000-lumen sodium-vapor lamp of similar construction, but slightly smaller in size and power consumption, and a 400-watt high-intensity mercury-vapor lamp are also available. Further details can be obtained from the nearest General Electric sales office. (picture caption: "Cloverleaf"" intersection of the Revere Beach Parkway and Broadway) (picture caption: Sodium-vapor lighting on the Boston-Worcester Turnpike, Newton, Mass.)

TO ALL USERS OF HIGHWAYS:
Modern civilization is committed to the cause of preventing accidents and disease and of repairing the damage they inflict when they cannot be prevented, or when we fail to prevent them. We spend millions of dollars every year in sanitation work - for sewers, water supplies, quarantines, preventive medicine, and for hospitals and sanitariums. The expenditure is amply justified; numberless thousand of lives are saved.

In proportion to what we spend for other preventive measures, however, we do not deal so generously with a highly important life-saving agency - street and highway lighting. We invest millions in better reads, which are used to an increasing extent at night. The traffic over them is enormous; but, unfortunately, so is the toll of causalities that attends this use. Rural night traffic accidents inflict and estimated money damage in this country of $400,000,000 a year. Worse than that, this rural night traffic alone results in about 6000 fatal accidents and 160,000 non-fatal accidents annually. Traffic accidents take a terrible toll each year. During the 18 months we were engaged in the World War, 50,510 members of the A.E.F. were killed in action or died of wounds, and 182,674 were wounded. In the 18 months ending December 31, 1931, 53,650 persons were killed and 1,576,840 were injured in traffic accidents in our city streets and on our rural highways.

It is not sufficient to think about these figures; we should do something about them. And we can. We can install adequate lighting for about 10 per cent of the cost of an improved highway; and the annual cost of operating such a lighting system is approximately 5 per cent of the cost of the improved highway.

Statistics show that for every thousand dollars of lighting cost, there is an economic saving of more than two thousand dollars by prevention of deaths and accidents.

Engineers have worked successfully on this problem. We have suitable equipment to light highways adequately. One of the latest lighting units for this purpose is the new sodium-vapor lamp described in this publication. Its soft, golden-orange glow, its lack of glare, adapt it admirable to give maximum comfort and safety in driving.

The need for adequate highway lighting is obvious. The physical means of obtaining it are available. Let's unite in an effort to combat a menace to public comfort and safety that looms greater year by year.

I can offer no better summary than that given by Osborne S. Mitchell, Editor, Electrical News and Engineering:

1. To the nation, it would mean greatly improved transportation facilities at little extra cost. In addition, it would mean a great saving in life and a large saving in what is now a direct economic loss amounting to millions of dollars annually.
2. To the farmer, where there are no existing distribution lines, it would mean electrification with all its increased efficiency on the farm.
3. To the motorist, it would mean fewer accidents and less nervous tension.
4. To the central station, it would mean lower overhead on rural lines.
5. To the states, it would mean fewer crimes and less policing, and greatly increased tourist traffic.
6. To the electrical industry, it would bring a large potential rural market.

M.O. Troy, MANAGER
CENTRAL STATION DEPARTMENT
GENERAL ELECTRIC COMPANY


* Following the successful demonstration of sodium-vapor lighting with 4000-lumen lamps on the Balltown Road, Schenectady, N.Y., in June, 1933. 


Original Caption by Science Service
General Electric



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