Electrical Notes.

Progress, Volume IV, Issue 8, 1 June 1909, Page 272

Electrical Notes.

The use of a tiny gas flame or a platinum point heated to incandescence by a circuit has long been used to engrave glass by the decrepitation of small pieces, and this property may be used to a more practical extent and on a larger scale in rock cutting in tunnels and in mining. A series of electric arcs on a turret at the heading is proposed for the purpose. The first attempt to pierce Hoosac Mountain in north-western Massachusetts was by means of a gigantic turret carrying numerous chisels, the invention of Gen. Herman Haupt, but, after boring a hundred feet or so, the machine was abandoned and the 4.71 miles of tunnel made by drilling and blasting. It was a long time before this tunnel was lighted by electricity, as there was not at the time any insulated wire in the market which would resist the dampness of the tunnel. From a Belgian report of the progress of electro-metallurgy it appears that the cost of simple fusion of steel in an electric arc furnace of 1% tons capacity is about £5 per ton, if the cost of electric energy is 2 cents per kilowatt hour. In large nonelectric steeel furnaces the cost of fusion is slightly greater than this, and in small coke furnaces it is more than twice as great. The electric furnace produces steel of very high grade and of any desired character, as the temperature can be controlled perfectly. The percentage of sulphur has been reduced from 0.146 to 0.015 and that of lead from 0.12 to 0.005 by refining steel in the electric furnace. For an electric furnace of iy a tons capacity the total consumption of energy may be estimated at 1,000 kilowatt-hours per ton of steel if the charge is cold and about one-third as much if the charge is already fused. The thermal efficiency is very high, 50 or 60 per cent. Messrs. H. A. Smith and Co., of Cuba street, Wellington, are successful tenderers for the electric cable and copper wire for the annual supplies to the Wellington Corporation for the ensuing twelve months. They have just landed a Pritchett and Gola Accumulator set for the Eketahuna Town Council. ■J£ 3fe : ff Speech having been registered by telephonic impressions so as to be intelligible — the different words being distingxiishable by sight, M. Carbonnel, the French engineer who perfected the apparatus, is seek-

ing a practical means of making a telephone receiver give an automatic report of itself on a travelling film or sensitised band, taking down any message that may come in the absence of the proprietor. The largest induction motor in the world was started recently at Gary, Ind., where it is installed in a large rolling mill. The motor is rated to develop 6,000 horse-j ower. It is of the three-phase 25-cycle type, and two 2,000-kilowatt Curtis turbines generate the current necessary to operate it. The motor receives the current at 6,600 volts. By using a step-by-step controller starting at 1,350 volts, the motor was successfully started in the proper direction, coming to full speed in 45 seconds. a. * * The Health Department of Chicago is making experiments with one of the new "pay-as-you-enter" cars, with a view to installing a better ventilating system than is now to be had. This experimental car, as described in the Electric Railivay Journal, is provided with a duplicate ventilating and heating apparatus. The apparatus is located under the longitudinal end seats. Two fans are used, one of which sucks the foul air from the upper part of the car and discharges it under the car floor, while the other takes in fresh air through a screened opening five feet above the platform, draws it through the coils of a heater, and distributes it close to the floor under the seats. * * * It has often been suggested that a dynamo be used as a telephone relay by placing the field winding in the primary circuit and the armature winding in the secondary circuit, so as to reproduce in the latter the fluctuating current of the former. The principal objection to this system seems to lie in the design of a suitable collecting device, which will not produce any disturbing effects. The Electrical Revieiv and Western Electrician describes an invention which is adapted to overcome this difficulty. It consists in the use of a dynamo with the field winding and the armature winding stationary, while the only moving part is an indicator, which is magnetised by the field winding. This inductor has a natural frequency which is much higher than that of the telephone currents, so that each pulsation of the telephone current will correspond to a large number of alternations produced by the inductor. Tta variation of current in the primary circuit of the field winding does not change the frequency, but does change the amplitude of the armature currents. * * A diagram is published in a recent issue of the Electric Railway Journal of the relation of weight to seating capacity of forty-six different electric cars of modern design used in American systems for city or interurban traffic. From this diagram the majority of the cars fall within the limits as regards seating accommodation of from forty-five to sixty passengers, and as regards weight, from 12001b. to 15001b. per seat. The cars varied from 6251b. to 16031b. per seat. The latter weight octurred in a car with accommodation for sixty-four passengers. Another car, with only four seats less, weighed only 8541b. per seat The latter i<3 a wooden car, and the former a steel one, but both are cars for interurban servicp. Cars for city service

vary between 6251b. and 10891b. per seat. The list included a car with accommodation for seventy-one passengers, while the heaviest was one of 51.3 tons. * # *- The increased use of electricity on the Pennsylvania Railroad has led to a study of the dangers of handling live wires, and the methods that must be emploj^ed in resuscitating those who have been stunned by an electric shock. A special pair of pliers has been designed which enables a man to cut a live wire carrying 23,000 \olts without danger to himself. To remove the wire from a body when no other means are at hand, a coat is placed under the wire, and lifted by the sleeves, to raise the wire off the body. This was found perfectly safe, even when the garment was damp. Experiments with fire streams showed that there was no danger of the current flowing down the stream of water even from a high-voltage line when the operator held the nozzle at a distance of between three and four feet from the wire. Experiments with chemical extinguishers showed that they were very dangerous where a solid stream was played on the wire. * # # The United States Geological Survey is recommending the use of electric power in mines. The electrical equipment, however, must be installed with great care, so as to guard against danger of fire or shock. The underground voltage should not exceed 650 for direct current, or 500 for alternating current, and lower voltages are preferable. Where a higher voltage is used, it should be transmitted by a completely insulated cable. No live electric wire should be permitted in any part of the mine in which gas is found to the amount of two per cent. « •* * The Navy Department is considering the building of a long-distance wireless telegraph station near Washington which will nave a sending radius of 3000 miles. This station will supersede the present stations along the Atlantic coast. The Department also expects to call for bids on a pair of high-power ship equipments with sending radius of 1000 miles each. * * # A movement is on foot in- England to reduce cable charges to America and cut the rate between Englabd and the Continent 'to two cents a word. The idea is to "h ! a.ve the various governments obtain control of the cables, and thus permit their use at the lowest possible figures. No doubt this movement will result in considerable complication, owing to 1 the international agreements that would be required. * * * In making a review of the present use of electric furnaces in the iron and steel industries, Mr. J. B. C. Kershaw, in a recent issue of the Iron Trades Review, stated that such furnaces were now in use in altogether forty-one places in France, Germany, Austria, Switzerland, Italy, Spain, Sweden, the United States of America, Canada and England. According to a recent article in Stahl und Eisen, there are in use altogether 78 electric furnaces, of which 14 are of the Kjellin type, 10 of the Rochling-Rodenhauser, 19 of the Heroult, 10 of the Girod. and 11 of the Stassano type, besides various others, of which only one or two examples are as yet in use.