New Power Installations.
Several new hydroelectric stations have gone into service during the year. Among these is the Clayton station of the Appalachian Electric Power Co. (American Gas and Electric Co.), which involves four 20,333 kilovolt-ampere alternators. The entire station was designed with the modern architectural motif in view. For example the contours of the turbines and generators were streamlined, the color scheme of the station is attractive and the enormous block glass windows have a strong architectural appeal.
Two more 82,500-kilowatt units were placed in service at Boulder Dam making the seventh and eighth units, and work is now being conducted on the ninth and tenth units. Three 108,000-kilowatt alternators are being constructed for Grand Coulee. These are 48.5 feet in diameter, which is larger than the Boulder Dam alternators and the largest water-wheel-driven alternators yet constructed.
The first unit of the Bonneville Power substation on the Columbia River, located one mile north of Vancouver, Wash., has been completed and preparations are under way to distribute the power in that region. There are two 230,000-volt, 3-phase, 60-cycle incoming transmission lines from Bonneville Dam. There are plans for one outgoing 230,000-volt line to the Puget Sound area and six 115,000-volt lines to other points in Washington and Oregon.
The Michigan Electric Co. placed in service, late in 1939, at New Carlisle, Indiana, a 25,000-kilovolt ampere, 3600-rpm, synchronous condenser manufactured by the Westinghouse Electric & Mfg. Co. This is the first large-sized synchronous condenser built for the high-speed of 3,600 rpm. The high speed permits small size and weight. It is hydrogen cooled and its direct-current excitation is obtained by means of an ignitron (mercury-arc) rectifier. This is an innovation since heretofore synchronous condensers have commonly been excited from a small exciter consisting of a direct-current generator driven by or mounted on the shaft, or from direct-current bus-bars. A synchronous condenser is an alternator operating as a synchronous motor without shaft load. By overexcitation (dc) the synchronous condenser may be made to take a leading current just as a static condener or capacitor. By underexcitation it may be made to take a lagging current just as a reactor or inductance. Such condensers are essential to control the voltage on high-voltage transmission lines such as that from Boulder Dam to Pasadena.
Another 60,000 kilovolt-ampere hydrogen-cooled synchronous condenser was installed in the Chino substation of the Southern California Edison Ltd. This and a similar unit installed a year ago are used to control the voltage of the long incoming lines from Boulder Dam.
The three largest autotransformers ever built were installed on the system of the City of Los Angeles. Each covers a ground space of 24 by 12½ feet and each is over 37 feet high. The bushings are the largest yet in use, being 24 feet, 3 inches long. These autotransformers will step down power from the 287,000-volt Boulder Dam line to 138,000 volts, for local transmission. The autotransformers are rated at 65,000 kilovolt-amperes and have the remarkably high efficiency of 99.64 per cent. (See also WATER POWER.)
The Amplidyne.
Dr. E. F. W. Alexanderson, A. F. Fisher and M. A. Edwards of the General Electric Co. have developed a new type of power generator known as the Amplidyne, which is capable of operating as an amplifier of control impulses in much the same manner as the vacuum-tube amplifier acts, but the Amplidyne operates at much higher power levels. It responds almost instantly to changes in power input with no appreciable lag between input control and output response. A total amplification of 10,000 to 1 is possible. The Amplidyne consists of a motor-driven generator with an extra set of short-circuited brushes for each pair of poles, these brushes being at right angles to the power brushes. The control magnetic field is energized by a field winding, and this magnetic field induces a voltage in the short-circuited brushes with an over-all amplification of 100 to 1. The current in the short-circuited brushes, reacting through the armature, produces a further amplification of 100 to 1 at the power brushes, resulting in a total amplification of 10,000 to 1. There have been several installations of the Amplidyne generator, particularly in the steel industry, the object being to secure rapid and accurate positions of the tool in a boring mill, and to control the speed of reeling continuous steel strip. In the paper industry an Amplidyne operating in conjunction with photoelectric devices permits the production of light and heavy weights of paper, and in addition maintains the exact register of paper moving through rewinding.
Electric Power in Modern Transport Planes.
The modern passenger airplane requires 15 kilowatts of electrical power as compared with 2 kilowatts in 1929. Of this power 7.0 per cent is used for operating the ship, that is for controls, etc.; 73 per cent is used for navigation including radio and de-icers; the remainder is used for service, mostly lighting. Two generators attached to the engines provide the current at 12 volts for charging storage batteries. The tendency at present is towards the use of a 24-volt system.
Mercury-Arc Rectifiers.
Aluminum is made by electrolyzing alumina (Al2O3) in an electric bath of fused cryolite (a fluoride of sodium and aluminum, Na3Al F6). This process requires a large direct current in the neighborhood of 10,000 amperes at a voltage of from 6 to 10 volts per cell. Until recent years, the direct current (dc) has been supplied by direct-current generators and more particularly by synchronous converters which convert alternating current (ac) into direct current. For the past few years the mercury-arc rectifier has been superseding these rotating machines for conversion of ac to dc for such power purposes as direct-current power systems and railway electrification such as the Lackawanna Railroad. However, recently a large mercury-arc rectifier unit has been built by the General Electric Co. for the new reduction plant of the Aluminum Company of America at Vancouver, Washington. The complete unit is rated at 10,000 amperes, 600 volts, dc, and comprises 12-anode ignitron rectifiers with a main transformer and reactors. In the past mercury-arc rectifiers have been built with the three, six or twelve anodes in a single steel tank. With such conventional multiple-anode rectifier tanks the arc drop increases with the number of anodes and as a result the efficiency decreases. The ignitron rectifier is designed to overcome this disadvantage. It consists of a single-unit mercury-arc rectifier with one anode and one cathode. Since a single ac mercury-arc is not self-sustaining, a high resistance rod dipping into the mercury pool and energized at the proper instant every cycle, starts the arc each cycle.
The Allis-Chalmers Co. has devised a single-anode tank mercury-arc rectifier which differs from the ignitron in that a continuous arc is used for establishing the arc each cycle rather than an ignitron which produces intermittent excitation. The igniter-exciter which produces the arc does not need to be immersed in the mercury pool and the level of the pool is not critical. Grids and shields are designed to provide adequate deionization and baffling. For service below 1,000 volts dc the efficiency of this rectifier is substantially greater than that of the multiple-anode type.
Oil-Less Circuit-Breakers.
There is an increasing trend to the use of oil-less or air circuit-breakers for indoor service. The advantage of air circuit-breakers is the elimination of the fire hazard and the maintenance caused by the carbonization and deterioration of the oil. By the use of compressed air the interrupting capacities of air circuit-breakers have been carried to the unheard of value of 1,500,000 kilovolt-amperes, about twice the value obtained with European breakers. This is accomplished by using a blast of air at 150 pounds per square inch pressure driving the arc against a series of splitter plates. Records have been obtained which show an interrupting capacity of 60,000 amperes at 13,500 volts, single phase. The very high speed of operation is due to the fact that the air also serves to operate the breaker mechanism. This also improves the performance since there are no heavy springs to oppose the closing of the breaker. The operation of these breakers is very fast, there rarely being more than a half-cycle of arcing.
Also along parallel lines, experiments have been conducted with water as the extinguishing medium, which show that this type of breaker can be built successfully to interrupt 1,500,000 kilovolt-amperes. Both the air and water circuit-breakers are small enough to fit into the cell structure of oil-breakers of the same rating.
A new type of air breaker designed for from 2,500 to 5,000 volts operates on the principle of driving the arc by means of an intense magnetic field into a series of slots in a narrow dead-end pocket formed from non-gas-forming material. The ionized arc gas is caused to intermingle with the non-ionized gas, causing deionization and rapid extinguishing of the arc.
Oil Circuit-Breakers.
Many improvements have been made in oil circuit-breakers, resulting in decreased size, and increased rapidity in the operation of the operating mechanism. Such breakers have an interrupting time as low as 5 cycles. Also improvements have been made in accessibility which is advantageous both in the wiring and in maintenance.
Underground Cables.
The electric conductors in high-voltage power cables and in telephone cables are insulated with paper tapes. In the former the paper tapes are impregnated with an insulating oil while in the telephone cables they are dry. The continued operation of both types of cable depends on the integrity of the sheath. One of the greatest causes of sheath failure has been the imperfect die welds along the sheath. The sheath is formed by a ram or plunger acting in a press cylinder to force the hot lead through a die to form the cylindrical sheath. The imperfect die welds are caused by the oxides and impurities which form on the surface of the molten lead in the press cylinder and remain when a new charge is added. Hence the die weld formed between the old and new charges is weakened by the presence of oxides and impurities in the weld. The General Electric Co. has eliminated this difficulty by the following means: The new molten charge is kept under an atmosphere of inert air to prevent oxidization; it is introduced into the press cylinder as molten lead flowing through a spout that goes well into the bottom of the cylinder, and at the end of the spout there is a nozzle that imparts a swirling motion to the molten lead that frees the oxide from the surface of the old charge. The oxides being lighter than the lead rise to the surface and the cylinder is allowed to overflow so that the oxides go out into a flood ring at the top of the cylinder. A hydrogen flame playing into the top of the cylinder prevents oxide forming when the ram is withdrawn from the cylinder. Examinations of the die welds made with this new process show no imperfections.
Activated Carbon Tapes.
The most radical development in high-voltage cable construction was the description given at the Convention of the American Institute of Electrical Engineers at Swampscott by S. J. Rosch of the Anaconda Co., of an activated carbon tape adjacent to the conductor in impregnated-paper-insulated cables. One of the principal factors in the failure of such cables is the evolution of gas from the paper and impregnating oils under the conditions of heating and stress during service. Oxygen is particularly destructive. The gases form voids in the cable, ionization occurs in the voids resulting in a gradual disintegration of the insulation. The activated carbon absorbs these gases and experiments under service conditions show that the life of the cable is prolonged.
With the laying of a 5-mile length of 22,000-volt cable between Falmouth and West Chop, Mass, the Cape and Vineyard Electric Co. provided a new source of electrical energy for its customers on the Island of Martha's Vineyard, heretofore dependent on the 1,625-kw Diesel-electric station at Oak Bluffs. At Falmouth the connection is made with the Affiliated New Bedford Gas and Edison Light Co. which is the principal power source in southeastern Massachusetts and the Cape Cod area.
Insulated Wire.
The General Electric Co. has developed a radically new type of enamelled magnet wire called Formex. The wire is insulated with a polyvinyl-acetal type resin and is distinguished by the adherence, stretchability and great mechanical toughness of the film. A coil of Formex insulated wire that was stretched 20 per cent in length was then wound on a mandrel of its own diameter without the insulation cracking. Formex is superior to enamelled wire in abrasive resistance, in resistance to solvent attack and freedom from heat cracking. The wire has already found several applications, particularly in small motors.
Lightning.
In 1939 the Westinghouse Co. devised the 'fulchronograph' which consists essentially of an aluminum disc a foot in diameter around the edge of which are inserted 400 hard-steel fins each about one-half the size of a nail file. Every 1/25,000 of a second a fin passes a narrow coil through which the lightning current passes and the fins accordingly become magnetized. From the degree of magnetization of the several fins, which is determined in the laboratory, not only the magnitude of the current in the lightning surge can be determined but the entire wave can be plotted as a function of the time.
During the past year the Westinghouse Co. has installed several of these instruments in the top of high buildings and have obtained many interesting records of lightning discharges.
The research on lightning conducted by the General Electric Co. in the top of the Empire State Building continues and during the year a paper was presented describing the multiple nature of lightning strokes.
Illumination.
The general adoption of the sealed-beam headlight was an outstanding development in the art of illumination during the past year. No other major safety step in motor cars has had such a widespread initial adoption. Almost all 1940 cars are equipped with completely interchangeable sealed-beam headlights designed to the same optical specifications. There are two interchangeable forms, an all-glass unit in which the filament operates directly in the unit without a bulb of its own and a unit with a metal reflector in which the lamp with its bulb is permanently affixed to the reflector and the lens sealed to the reflector. The sealed-beam type of headlight has many advantages; higher light output with more coverage laterally and vertically; substantial reduction in glare to oncoming drivers and at the same time illuminating the right-hand side of the road to a greater distance; lighting efficiency maintained at a high value during the life of the lamp with new-car efficiency with the installation of a new unit; simple and uniform provision for aiming headlight readily carried out by car owner; uniform beam indicator; ready availability of renewal units through standardization of the interchangeable forms.
In fluorescent lighting a new white color was developed for all sizes of fluorescent lamps. In the newer equipment the lamps are shielded from direct view, direction or diffuse distribution being provided as desired. In previous units the auxiliaries included both ballast and automatic switch so that a faulty switch required opening the wire channel and replacing the complete auxiliary. In the later units the ballast and switch are separate and the latter is easily accessible so that it is readily replaceable.
A 6-watt, 9-inch lamp has been put on the marked designed particularly for air liners and Pullman berth. It is available both in white and daylight.
The tellurium lamp, a new type of electric lamp employing tellurium vapor, has been developed by the Westinghouse Lamp Works at Bloomfield, N. J. The actual light comes from a glass tube shaped like an inverted J, which is contained in a larger glass bulb. With a tube four inches long and a little more than a half-inch in diameter, satisfactory operation was secured with 2 to 3 amperes of current at 150 to 200 volts. The tellurium resembles a glowing solid more than a glowing gas and the light is close to daylight.
A new photoflash lamp smaller than a golf ball has been added to the line of flash lamps. It is designed for all purposes except focal-plane-shutter cameras and two dozen can be carried easily in a suit pocket. It gives a million lumens at the peak of the flash and it is provided with a bayonet-type base designed for rapid loading and unloading. (See also PHOTOGRAPHY.)
The 1,000-watt, water-cooled mercury lamp — the midget sun — of a year ago has been considerably improved as regards the water jackets and in the safety circuits and auxiliaries. The 100-watt capillary mercury lamp has been put into an ultraviolet transmitting bulb, making it an excellent sun lamp. It is expected to be very useful in the animal and poultry industry.
Street Lighting.
The highest level of illumination along urban business streets is now in Falls Street, Niagara Falls, N. Y. Twin light standards with 15,000-lumen series lamps are arranged opposite and on approximately 70-foot linear spacings with a mounting of 23 feet above the street. The average lighting on the pavement is more than 5 foot-candles, a sufficient intensity for the reading of ordinary sized type.
The world's largest and longest sodium safety-lighting system was turned on and dedicated in July. It constitutes the 33-mile Belt Parkway running from Owl's Head Park in Brooklyn to the Bronx-White-stone bridge in Queens. More than 2,200 lights developed by the General Electric Co. are used. The luminaires employ airplane-shaped reflectors and use 10,000-lumen lamps in a horizontal position. They are mounted 23 feet above the Parkway on cedar poles spaced 150 feet apart along a divided highway. Incandescent 230-watt lamps with orange-colored glass globes to harmonize with the sodium lights are installed in the ceilings of the underpasses.
Germicidal Lamp.
The General Electric Co. has invented a new germicidal lamp which differs materially from those heretofore in use in that it is inexpensive, of low wattage, and does not generate any great amount of heat. The lamps heretofore in use for germicidal purposes were either carbon or iron arcs or mercury arcs in quartz tubes and of relatively high wattage such as 250 watts. The new lamps are available in 3-, 5- and 15-watt sizes; about 95 per cent of their ultraviolet light is effective in killing germs. The 3-watt lamp is about 5½ inches long; the 5-watt is about 9 inches long and the 15-watt lamp is 18 inches long. These lamps have the same operating characteristic as fluorescent lamps and the 15-watt size can be operated in a fixture for an 18-inch lamp. A small reactor is in series with the 3-watt size and a resistance is in the base of the 15-watt size. An aluminum reflector is needed to reflect the ultraviolet light. An idea of the effectiveness of these lamps is evidenced by the fact that a 15-watt lamp will kill B-coli at a distance of one meter in 30 seconds. The uses of such lamps are many. They are used for sterilizing the air-ducts of air-conditioning systems; for the prevention of mould in food; for killing germs in soda-water glasses and dishes; to prevent rickets in poultry, and in hospitals.
X-Ray Equipment.
The most powerful and most flexible X-ray equipment of its type has been installed in the new high-voltage laboratories of the National Bureau of Standards at Washington, D.C. The outstanding feature is the means by which 1,400,000 volts, direct current, is obtained. The main high-voltage generator involves several new features. It consists of a ten-section cascade stack of oil-filled Herkolite cylinders, the base of each section securely bolted to the next and at each base there is a shielding ring. The entire stack is filled with oil. In each section there is a 140,000-volt (dc) unit consisting of a main transformer, a filament transformer, two kenotron rectifiers, and two 0.1-microfarad capacitors. The main transformer in each section has two tertiary high-voltage windings, one of which supplies the primary of the transformer in the next section and the other supplies the kenotron filaments. The entire assembly is 30 ft. 6 inches high including the corona cap and occupies very little floor space. Adjacent to the generator stack is a smaller Herkolite stack of the same height containing a high-voltage resistance potentiometer. The generator feeds potential to a third stack containing the X-ray tube, connections being made from the shielding rings on the generator to corresponding rings on the X-ray stack and also to the potentiometer stack.
New Electron Microscope.
The magnification which can be obtained by optical means is limited by diffraction and is from 3,000 to 6,000 diameters, depending on the specimen. Also the length of light waves themselves limits the size of objects which can be resolved by the ordinary microscope. A beam consisting of moving electrons, although it cannot be focused by means of glass lenses, may be focused by being passed through lens-shaped magnetic fields and a high degree of resolution thereby obtained. This is the principle of the electron microscope. The specimen must however consist of a very thin film through which the electrons may pass quite readily. The microscope consists of a long tube at a very high vacuum containing an electron source with the accompanying accelerating potentials (electron gun) and three focusing coils and the projection coil. The specimen is placed within the objective coil. After the beam passes through the specimen the objective coil produces a magnification of 100 times and the beam is then directed through the projection coil which produces further magnification of 250 times, making a total magnification of 25,000 diameters. At the bottom of the tube there is either a fluorescent screen on which the image may be viewed or a photographic plate to record the image. It should be pointed out, however, that in a sense the image produced by the electron microscope is a shadowgraph and may not disclose factors than can be revealed by the optical microscope.
No comments:
Post a Comment