1938: Electrical Engineering

Electrical Power and Machinery.

A 22,500-kw. turbine-generator has been brought out which operates with 2,300-lb, steam pressure nearly double that of the high-pressure plants now installed in this country. The use of hydrogen-cooled alternators has continued to expand, and there are now approximately 1,000,000 kw. either installed or under construction.

Turbine-alternator units with ratings of 53,000 and 50,000 kw. at 3,600 r.p.m. have been put in service, the former at the Waterside plant of the Consolidated Edison Company of New York. Prior to 1937 no unit larger than 18,000 kw. had operated at higher speed than 1,800 r.p.m. Also, these units involve the superposition principle whereby a low-pressure turbine takes steam at 200 lb. from the exhaust of the main unit, which operates at 1,200 lb., and expands the steam to 60-lb. and 5-lb. gage for feed-water heaters. This gives an efficient method of obtaining feed-water at a sufficiently high temperature for the 1,200-lb. boiler.

A radical change in transformer construction is brought out in the new distribution transformer of the General Electric Company, in which the magnetic circuit, instead of consisting of hundreds of hand-assembled flat laminations, is made of a continuous, machine-wound steel ribbon in the form of a tightly wound coil. The primary and secondary windings are clamped together, and ribbon coils are then wound by machine about them. For each primary-secondary group, two coils of steel ribbon are used, each one encircling the opposite side of the coil assembly. With this construction, the active magnetic material is used more effectively; the clamping structures are simplified; and the sizes, weights, and total losses are reduced.

Steel-tank mercury-arc rectifiers have practically superseded rotating machinery, such as motor-generator sets and synchronous converters in new installations, for the conversion of alternating to direct current. This is due to their higher efficiency, lesser weight, and floor space. Such rectifiers have replaced the synchronous converters which supplied power for the Baltimore and Ohio trains in the Belt Line which includes the 1.4-mile Howard Street Tunnel into Baltimore. A street extension necessitated a change in location of the substation. The only railroad-owned space in the immediate vicinity was land directly over the tunnel. It was doubtful if the wall of the tunnel would support the weight of the rotating machinery of the existing substation. Hence a new station having mercury-arc rectifiers was built. Another great advantage of this change was that the old station could supply power until the new one was ready for service. The installation consists of two 3,000-kw. rectifiers that supply 670 volts direct current to the railroad feeders.

In the past, resistors for outdoor service particularly, have been made of cast iron. Such resistors are more or less fragile, the assembly is mechanical; many times the resistors prove inadequate electrically, and cast iron corrodes readily. For service where such resistors have proved to be inadequate, a resistor made of stainless steel ribbon has been devised. The ribbon is wound in zig-zag form over expansion insulating members, which are supported on a frame. With such a resistor, the maintenance and depreciation are practically nothing, even when it is used out-of-doors. Stainless-steel resistors are being used for outdoor service at power stations and are well adapted to controller resistors for railway and railroad equipment, where the resistors are exposed to the weather.

Transmission.

Experience and exhaustive tests have demonstrated the effectiveness of the De-ion Protector Tube in protecting transmission lines against lightning and power arcs. The protector is merely a fiber tube with an electrode and ferrule at each end; and the length of tube is so adjusted that the impulse breakdown, such as occurs with a lightning stroke, is less than that of the insulation to be protected. The protector is usually applied in a vertical position directly below the line conductor, which is suspended at the lower end of an insulator string. An arc-shaped bar is attached to the upper end, just below the conductor and at right angles to it. The distance between the upper ferrule of the protector and the conductor is adjusted to give the proper length of gap for the line conditions. The lower electrode of the conductor is grounded solidly.

When a lightning stroke hits the conductor, it discharges through the tube to ground. The heat vaporizes gases from the organic material of the fiber tube. These neutral gases are expelled violently into the arc stream, de-ionizing and thus extinguishing the arc. This prevents the arc restriking because of the follow-up of power voltage of the system. The tube is simple, relatively inexpensive; and data collected on a large number of lines show that in systems equipped with this protector, outages due to lightning have been materially reduced.

Transportation.

The New York, New Haven and Hartford R.R. has put into service six 3,600 hp. stream-lined passenger electric locomotives to operate between New Haven and the Grand Central Station, New York. Each locomotive can haul a 1,200-ton passenger train at 80 miles per hour. They are the most powerful passenger locomotives now in service. The rated a.c. tractive effect is 24,200 lb.; continuous d.c. tractive effect is 26,900 lb.; total weight fully loaded is 432,000 lb.; and total length is 77 ft. The locomotive operates at either 11,000 volts a.c. with overhead trolley or at 600 volts d.c. with third rail. Since the locomotives must run into the Grand Central Station over the New York Central tracks, the locomotives must operate 600 volts, third rail as well as 11,000 volts a.c. with overhead trolley.

Progress has continued in the rehabilitation of city transportation facilities by the extended use of the Presidents' Conference trolley car and the trolley bus. A few diesel-electric buses, which are very recent developments, have been put in service, and their operation is being watched with interest. More diesel-electric stream-lined locomotives were added to railroad equipment. Also, two diesel-electric switching locomotives have been put in service; and because of their flexibility and standby economies, they are proving to be very successful.

The first aerial tramway to be erected on the North American Continent is now in operation on the slope of Cannon Mountain at Franconia Notch, New Hampshire. The profile of the famous Old Man of the Mountain is located on Cannon Mountain. Two comfortable 27-passenger cars suspended from cables carry passengers up the 5,400-ft, slope above the tree tops in six minutes. The cars are drawn along the main cables by slack cables operated by direct-current electric motors located in the valley station. The necessary power is supplied by a 100-hp. direct-current motor, which obtains its power from a direct-current generator driven by a 125 h.p. 440-volt, 3-phase induction motor. There is also available a 60-h.p. 1200-r.p.m. 6-cylinder gasoline engine for emergency service. One car ascends while the other descends. The electrically controlled operation is smooth and quiet. The tramway will operate in the winter for the benefit of those who ski.

Electric Illumination.

The General Electric Company has brought out a high-efficiency tungsten filament which permits a substantial increase in light output of incandescent lamps without any increase in the power taken by the lamp. For example, the new lamp in the 60-watt size gives more than to per cent more illumination than the older type, for the same energy input. The added efficiency is obtained by re-coiling the coiled filament. This reduces the filament area exposed to the gases in the bulb and hence reduces the cooling of the filament by the convection of the gases. For example, for a 60-watt, 115-volt lamp the tungsten wire, which is 1/10,000th of an inch diameter, and almost invisible to the naked eye, is wound around a molybdenum wire which serves as a mandrel, leaving the coils 1 1,000 inch apart but not touching each other. This coiled wire is then coiled again on a second mandrel with 70 turns to the inch and a spacing of 7 1,000th inch between coiled turns. The wire initially was 20 in, long. The first coiling compresses it to a length of 3.4 in, and the second coiling to only inch. Following the second coiling, the mandrel is dissolved chemically. A further increase in efficiency is obtained by the introduction of special gases.

The Sterilamp, made by the Westinghouse Electric and Manufacturing Company, is a tubular lamp designed to emit very short-wave radiation which destroys bacteria. It consists of a glass tube about 20 in, long, at the ends of which are electrodes with electron-emitting coatings. The tube contains mercury vapor and traces of other gases to improve the operating conditions. It requires 575 volts to start the are discharge, the current is 35 milliamp., and the power consumption is about 12 watts. The lamp is used in hospitals, particularly in the corridors and operating rooms, since the radiation destroys readily the bacteria that may be floating in the air. Experience shows that the Sterilamp, because it destroys harmful bacteria, accelerates the healing of tissue and in many cases prevents fever that would otherwise occur. The lamp is used in the packing of meats, foods, and allied products to sterilize the wrappings and containers. In bakeries, it destroys mould spores and thus reduces mould growth. The lamp should not be confused with 'health lamps' and should not be viewed with unprotected eyes.

Another outstanding development is the low-voltage fluorescent lamp. This consists of a tube of from 1 to 1 in. diameter and from 18 to 36 in. length, containing mercury vapor. A fluorescent powder on the inner walls converts the invisible ultra-violet short-waves into the longer wave-lengths visible radiation. By proper selection of the fluorescent powder, almost any desired color can be obtained; and for the first time, a practical source, matching daylight in appearance, is produced efficiently with low-power inputs. The lamp is energized with a hot cathode. The electrodes are small tungsten-coated coils with some material such as barium to improve their emissivity. It is desirable to heat the electrodes on starting. Hence an auxiliary circuit, which is cut out after starting, is provided. These lamps are very much more efficient than tungsten lamps, giving 50 to 200 times as much colored light per unit of energy as the tungsten lamps, and 60 to 75 lumens per watt white light, as compared with 15 to 20 for tungsten lamps. With these lamps it is possible to obtain colored lighting effects never before possible. They are being installed at both the New York 1939 World's Fair and the Golden Gate Exposition at San Francisco, and the nocturnal effects produced far surpass those of any recent fairs or expositions.

Both the San Francisco-Oakland bridge and the Golden Gate bridge, two of the world's largest, are illuminated with the new sodium-vapor lamps.

The year 1938 has seen extended developments in the use of floodlighting for evening performances of outdoor sports. Such floodlighting for football and baseball is becoming quite common. The illumination of Ebbets Field of the Brooklyn Dodgers baseball team in 1938 is the latest of these floodlighting developments. There are 615 huge floodlights, giving 92,000,000 candlepower, and the light intensity on the diamond is ten times that in the ordinary business office. This installation was very successful both from the standpoint of the amount and distribution of the illumination and from the point of view of the numbers who attended.

A new and extremely small photoflash lamp capable of producing a flash amply brilliant and 'flat' enough to meet the exacting needs of news camera men and other photographers is also among the lighting developments of 1938.

Electrical Industries.

Steel.

In the steel industry the tendency is toward the adoption of larger, faster, and more efficient machines. In size, the new 98-in, strip mill of the Republic Steel Corporation at Cleveland is predominating. The maximum delivery of the hot mill is 2,121 ft. per minute, and it can roll all finished widths from 30 to 94 inches and all finished thicknesses from 18-gauge strip to one-half-inch plate. The output is 70,000 gross tons per month. The hot mill requires almost 40,000 h.p. for the main drive motors alone. This development was made possible by recent improvements in hydraulics, welding, design of bearings, lubrication, and electrical control.

Cupaloy.

For years metallurgists have been attempting to develop a hardened copper which retains the high electrical and thermal conductivities of the metal itself. The different bronzes are reasonably satisfactory mechanically, but have low conductivity. An alloy, Cupaloy, 99.4 per cent copper, has been developed in the research laboratories of the Westinghouse Electric & Manufacturing Company, which has 90 per cent the electrical conductivity of copper and between 80 and 90 per cent of the thermal conductivity. The alloy contains a fraction of a per cent of chromium and a trace of silver. In the properties of hardness and tensile strength it is superior to hot rolled steel (0.25 per cent carbon) and has an elastic limit about eight times that of hard-drawn copper. It appears to have a number of possibilities, such as welding electrodes, slip-rings for dynamos, springs, and cylinder heads for internal combustion engines.

Woven Glass Insulators.

The year has seen a rapid increase in the use of woven glass, or Fiberglas, as an insulator. There are two general types: one made from relatively short fibers, 8 to 15 inches long, called staple; and the other a fiber continuous in length, like rayon, and called continuous. Woven glass, because of its superior mechanical characteristics and because of its greater compactness, is taking the place of asbestos in many applications of high-temperature insulation. It is used to insulate magnet wire and wires used at high temperature. Also, it is used advantageously in railway and mine motors, which are frequently subjected to high temperatures. Woven glass is made in the form of varnished cambric and also in combination with mica, although in each case the maximum temperature is limited in value by the organic resins that are used for coatings and impregnation.

Another outstanding development of the year as a result of research is an X-ray apparatus for operations, which operates at a half-a-million volts. Also an oil-immersed multisection X-ray which is shock-proof and semi-portable has been developed.

Air Conditioning.

Dust Precipitation.

High-voltage discharge for the precipitation of dust particles has long been used; but because of the high d.-c. voltages necessary, the relatively large amount of power, the space requirements, and the large amount of ozone generated, the method had limited applications. By much improved design, the Westinghouse Company has developed a small compact precipitator that can readily be used in the ordinary house air-conditioning unit. Tests show that even with very fine particles, such as smoke particles, the precipitator removes 99.5 per cent, which is much greater than is possible with filters and air washers.

Marine.

The highest steam pressure and the highest temperature yet used on any American-built ship were installed for two turbine-electric-driven tankers recently put into service. The steam pressure is 600-lb. gage, and the temperature is 825° F. Both tankers were built by the Sun Shipbuilding and Dry Dock Company, one tanker for the Atlantic Refining Company, and the other for the Tidewater Associated Oil Company. The first tanker is driven by a 5,000 h.p. a.-c. motor at 90 r.p.m., the power being supplied by a 4,500-kw. turbine generator.