Specifications for Lamps. (Crocker.) The initial candle-power of any lamp at the rated voltage should not be more than 9 per cent above or below the value called for. The average candle-power of a lot should be within 6 per cent of the rated value. The standard efficiencies are 3.1, 3.5, and 4 watts per candle-power. Each lamp at rated voltage should take within 6 per cent of the watts specified, and the average for the lot should be within 4 per cent. The useful life of a lamp is the time it will burn before falling to a certain candle-power, say 80 per cent of its initial candle-power. For 3.1 watt lamps the useful life is about 400 to 450 hours. for 3.5 watt lamps about 800, and 4 watt lamps about 1600 hours. Special Lamps. The ordinary 16 c.-p. 110-volt is the standard for interior lighting. Thousands of varieties of lamps for different voltages and candle-power are made for special purposes, from the primary lamp, supplied by primary batteries using three volts and about 1 ampere and giving c.-p., and the 34 c.-p. bicycle lamp, 4 volts and 0.5 ampere, to lamps of 100 c.p. at 220 volts. Series lamps of 1 c.-p. are used in illuminating signs, ampere and 12.5 to 15 volts, eight lamps being used on a 110-volt circuit. Standard sizes for different voltages, 50, 110, or 220, are 8, 16, 24, 32, 50, and 100 c.-p. Nernst Lamp. A form of incandescent lamp originated by Dr. Walther Nernst, of Göttingen, is being developed in this country by the Nernst Lamp Company, Pittsburg, Pa. It depends for its operation upon the peculiar property of certain rare earths, such as yttrium, thorium, zirconium, etc., of becoming electrical conductors when heated to a certain temperature; when cold, these oxides are non-conductors. The lamp comprises a "glower" composed of rare earths mixed with a binding material and pressed into a small rod; a heater for bringing the glower up to the conducting temperature; an automatic cut-out for disconnecting the heater when the glower lights up, and a "ballast" consisting of a small resistance coil of wire having a positive temperature-resistance coefficient. The ballast is connected in series with the glower; its presence is required to compensate the negative temperature-resistance coefficient of the glower; without the ballast, the resistance of the glower would become lower and lower as its temperature rose, until the flow of current through it would destroy it. Fig. 171a shows the elementary circuits of a simple Nernst lamp. cut-out is an electromagnet connected in series with the glower. When current begins to flow through the glower, the magnet pulls up the armature lying across the contacts of the cutout, thereby cutting out the heater. The The heater is a coil of fine wire either located very near the glower or encircling it. The glower is from 1/32 to 1/16 inch in diameter and about 1 inch long. The material of the glower is an electrolyte, so that this type of lamp is not well adapted for operation on direct-current circuits because of the wasting away at the positive end and the deposition of material at the negative end. Line Cut-out Cut-out Heater Glower Ballast The lamps are made with one glower, or with two, three, or six glowers connected in parallel, and for operation on 100 to 120 and 200 to 240 volt circuits. ELECTRIC WELDING. The apparatus most generally used consists of an alternating-current dynamo, feeding a comparatively high-potential current to the primary coil of an induction-coil or transformer, the secondary of which is made so large in section and so short in length as to supply to the work currents not exceeding two or three volts, and of very large volume or rate of flow. Other forms The welding clamps are attached to the secondary terminals. of apparatus, such as dynamos constructed to yield alternating currents direct from the armature to the welding-clamps, are used to a limited extent. The conductivity for heat of the metal to be welded has a decided influence on the heating, and in welding iron its comparatively low heat conduc tion assists the work materially. (See papers by Sir F. Bramwell, Proc. Inst. C. E., part iv., vol. cii. p. 1; and Elihu Thomson, Trans. A. I. M. E., xix. 877.) Fred. P. Royce, Iron Age, Nov. 28, 1892, gives the following figures showing the amount of power required to weld axles and tires: The slightly increased time and power required for welding the square axle is not only due to the extra metal in it, but a part to the care which it is best to use to secure a perfect alignment. TIRE-WELDING. 1 X 3/16-inch tire requires 11 H.P. for.. ........ Seconds. 15 25 30 40 55 62 The time above given for welding is of course that required for the actual application of the current only, and does not include that consumed by placing the axles or tires in the machine, the removal of the upset and other finishing processes. From the data thus submitted, the cost of welding can be readily figured for any locality where the price of fuel and cost of labor are known. In almost all cases the cost of the fuel used under the boilers for producing power for electric welding is practically the same as the cost of fuel used in forges for the same amount of work, taking into consideration the difference in price of fuel used in either case. Prof. A. B. W. Kennedy found that 21⁄2-inch iron tubes 4 inch thick were welded in 61 seconds, the net horse-power required at this speed being 23.4 (say 33 indicated horse-power) per square inch of section. Brass tubing re quired 21.2 net horse-power. About 60 total indicated horse-power would be required for the welding of angle irons 3 × 3 × 1⁄2 inch in from two to three minutes. Copper requires about 80 horse-power per square inch of section, and an inch bar can be welded in 25 seconds. It takes about 90 seconds to weld a steel bar 2 inches in diameter. ELECTRIC HEATERS. Wherever a comparatively small amount of heat is desired to be automatically and uniformly maintained, and started or stopped on the instant without waste, there is the province of the electric heater. The elementary form of heater is some form of resistance, such as coils of thin wire introduced into an electric circuit and surrounded with a substance, which will permit the conduction and radiation of heat, and at the same time serve to electrically insulate the resistance. This resistance should be proportional to the electro-motive force of the current used and to the equation of Joule's law : H=12Rt X 0.24, where I is the current in amperes; R, the resistance in ohms; t, the time in seconds; and H, the heat in gram-centigrade units. Since the resistance of metals increases as their temperature increases, a thin wire heated by current passing through it will resist more, and grow hotter and hotter until its rate of loss of heat by conduction and radiation equals the rate at which heat is supplied by the current. In a short wire, before heat enough can be dispelled for commercial purposes, fusion will begin; and in electric heaters it is necessary to use either long lengths of thin wire, or carbon, which alone of all conductors resists fusion. In the majority of heaters, coils of thin wire are used, separately embedded in some substance of poor electrical but good thermal conductivity. The Consolidated Car-heating Co.'s electric heater consists of a galvanized iron wire wound in a spiral groove upon a porcelain insulator. Each heater is 30% in. long, 8% in. high, and 65% in. wide. Upon it is wound 392 ft. of wire. The weight of the whole is 23% ibs. Each heater is designed to absorb 1000 watts of a 500-volt current. Six heaters are the complement for an ordinary electric car. For ordinary weather the heaters may be combined by the switch in different ways, so that five different intensities of heating-surface are possible, besides the position in which no heat is generated, the current being turned entirely off. For heating an ordinary electric car the Consolidated Co. states that from 2 to 12 amperes on a 500-volt circuit is sufficient. With the outside temperature at 20° to 30°, about 6 amperes will suffice. With zero or lower temperature, the full 12 amperes is required to heat a car effectively. Compare these figures with the experience in steam-heating of railwaycars, as follows: 1 B.T.U. 0.29084 watt-hours. 6 amperes on a 500-volt circuit = 3000 watts. A current consumption of 6 amperes will generate 3000 0.29084 = 10,315 B.T.U. per hour. In steam-car heating, a passenger coach usually requires from 60 lbs. of steam in freezing weather to 100 lbs. in zero weather per hour. Supposing the steam to enter the pipes at 20 lbs. pressure, and to be discharged at 200° F., each pound of steam will give up 983 BT.U. to the car. Then the equivalent of the thermal units delivered by the electrical-heating system in pounds of steam, is 10,315÷983 = 10%, nearly. Thus the Consolidated Co.'s estimates for electric-heating provide the equivalent of 10 lbs. of steam per car per hour in freezing weather and 21 lbs. in zero weather. Suppose that by the use of good coal, careful firing, well-designed boilers, and triple-expansion engines we are able in daily practice to generate 1 H.P. delivered at the fly-wheel with an expenditure of 21⁄2 lbs. of coal per hour. We have then to convert this energy into electricity, transmit it by wire to the heater, and convert it into heat by passing it through a resistance-coil. We may set the combined efficiency of the dynamo and line circuit at 85%, and will suppose that all the electricity is converted into heat in the resistance-coils of the radiator. Then 1 brake H.P. at the engine 0.85 electrical H.P. at the resistance-coil = 1,683,000 ft.-lbs. energy per hour = 2180 heatunits. But since it required 21⁄2 lbs. of coal to develop 1 brake H.P., it fol lows that the heat given out at the radiator per pound of coal burned in the boiler furnace will be 2180 + 21⁄2 872 H.U. An ordinary steam-heating system utilizes 9652 H.U. per lb. of coal for heating; hence the efficiency of the electric system is to the efficiency of the steam-heating system as 872 to 9652, or about 1 to 11. (Eng'g News, Aug, 9, '90; Mar. 30, '92; May 15, '93.) = ELECTRICAL ACCUMULATORS OR STORAGE BATTERIES. The original, or Planté, storage battery consisted of two plates of metallic lead immersed in a vessel containing sulphuric acid. An electric current being sent through the cell the surface of the positive plate was converted into peroxide of lead, PbO2. This was called charging the cell. After being thus charged the cell could be used as a source of electric current, or discharged. Planté and other authorities consider that in charging, PbO, is formed on the positive plate and spongy metallic lead on the negative, both being con verted into lead oxide, PbO, by the discharge, but others hold that sulphate of lead is made on both plates by discharging and that during the charging PbO2 is formed on the positive plate and metallic Pb on the other, sulphuric acid being set free. The acid being continually abstracted from the electrolyte as the discharge proceeds, the density of the solution becomes less. In the charging operation this action is reversed, the acid being reinstated in the liquid and therefore causing an increase in its density. The difference of potential developed by lead and lead peroxide immersed in dilute H2SO4 is about two volts. A lead-peroxide plate gradually loses its electrical energy by local action, the rate of such loss varying according to the circumstances of its preparation and the condition of the cell. In the Faure or pasted cells lead plates are coated with minium or litharge made into a paste with acidulated water. When dry these plates are placed in a bath of dilute H2SO4 and subjected to the action of the current, by which the oxide on the positive plate is converted into peroxide and that on the negative plate reduced to finely divided or porous lead. The initial electro-motive force of the Faure cell averages 2.25 volts, but after being allowed to rest some little time it is reduced to about 2.0 volts. The "chloride" accumulator, made by the Electric Storage Battery Co., of Philadelphia, consists of lead plates containing cells filled with spongy lead or with lead peroxide. The spongy lead is formed by first casting into the lead plate pastilles of a mixture of lead and zinc chlorides, the lead in which is afterwards by an electrolytic method converted into spongy Plates intended lead, while the zinc chloride is dissolved and washed away. for positive plates have the spongy lead converted into peroxide by immersing them in sulphuric acid and passing a current through them in one direction for about two weeks. The following tables give the elements of several sizes of "chloride" accumulators. Type G is furnished in cells containing 11-125 plates, and The voltage of cells type H from 21 plates to any greater number desired. of all sizes is slightly above two volts on open circuit, and during discharge varies from that point at the beginning to 1.8 at the end. Accumulators are largely used in central lighting and power stations, in office buildings and other large isolated plants, for the purpose of absorbing the energy of the generating plant during times of light load, and for giving it out during times of heavy load or when the generating plant is idle. advantages of their use for such purposes are thus enumerated: The 1. Reduction in coal consumption and general operating expenses, due to the generating machinery being run at the point of greatest economy while in service, and being shut down entirely during hours of light load, the battery supplying the whole of the current. Outside meas'm't: 52 66 66 Normal charge rate.... 10 Weight each element, lbs. (Width, in., 66 23 33 ber 8% 8% 8% jar. 11 Weight of acid in glass jars in lbs. Weight of acid in rubber jars in lbs..... Weight of cell complete, with acid, in rubber jar in lbs.. Height of cell over all, in inches... 11 62 71 186 61% 74 82 11 9 160 180 70 80 190 106 125 145 165 184 15 15 15 1734 1734 1734 1734 105% 105% 12 9% 126 121 121% 1234 114 15% 15% 15% 15% 117 21 25 27 35 34 53 61 58 170 TYPE "G." Size of Plates, 15% × 151⁄2 in. 60 15 17 70 184 98 112 126 80 100 120 140 30 35 40 1634 183 20 104 114 124 302 339 376 415 18 18 19 19 19 219 260 300 341 503 2538 20.4 790 866 942 4741 38 Outside (Width. 15% 1634 183% 20 measurement 2758 1111 Length 1934 1934 1934 1934 2034 21% in ..160 179 197 216 292 1242 Weight of acid Height of cell over all, .... 42% 42% 42% 43% 9.5 515 552 590 2512 19.2 தீ 482 552 621 689 992 4560 36 1635 1769 1904 8696 68 26 26 26 26 29. 45 45 45 46 *D addition per plate from 25 to 125 plates; approximate as to dimensions and weights. 2. The possibility of obtaining good regulation in pressure during fluctua tions in load, especially when the day load consists largely of elevators and similar disturbing elements. 3. To meet sudden demands which arise unexpectedly, as in the case of darkness caused by storm or thunder-showers; also in case of emergency due to accident or stoppage of generating-plant. 4. Smaller generating-plant required where the battery takes the peak of the load, which usually only lasts for a few hours, and yet where no battery is used necessitates sufficient generators, etc., being installed to provide for the maximum output, which in many cases is about double the normal output. |