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American Institute of Electrical Engineers, Transactions of the

Volume XXXIII: 1914

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Displaying Results 1 - 25 of 54
  • Index

    Publication Year: 1914 , Page(s): ix - xiv
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  • Sphere Gap Discharge Voltages at High Frequencies

    Publication Year: 1914 , Page(s): 973 - 1012
    Cited by:  Papers (1)
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    The paper describes a series of experiments made by the authors to determine the values of steady high-frequency, high-voltage currelnts required to discharge between seven-inch copper spheres in air, at ordinary temperatures and barometric pressures. A 15-kw. arc generator was used as the source of high-frequency sustained high voltage, and the apparatus employed in securing and measuring currents of 123,000, 255,000 and 612,500 cycles is described in detail. The sphere-gap standard consisted of electrolytic copper spheres mounted on the ends of brass tubes in treated wooden frames, and the gap lengths were accurately determined by means of calipers and micrometer screw or steel scale. The results obtained are given in Tables II and III and are also charted in curves I and II, Fig. 5. The 123,000-cycle values show a right-line relation between sphere gaps and discharge voltage, which line, when extended, passes through the origin. The high-frequency voltages are almost uniformly 4.5 kv. below the 25-cycle voltages observed by Chubb and Fortescue. View full abstract»

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  • The Electric Strength of Air-V

    Publication Year: 1914 , Page(s): 951 - 972
    Cited by:  Papers (2)
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    The paper presents the account of an investigation of the influence of frequency on the corona, between 60 and 3000 cycles per second. The wire and coaxial cylinder method was used. A simple method for measuring the maximum value of an alternating voltage wave has been developed and used for obtaining this maximum value at the critical corona voltage. The gold-leaf electroscope was used to detect the first appearance of corona. It has been found that for frequencies above 275 cycles per second the corona voltage (maximum value) is not so uniform and constant as it is at frequencies in the neighborhood of 60 cycles. The indications of the investigation are that at 2000 cycles the corona voltage is lower than it is at 60 cycles by about 3 or 4 per cent. The experiments reveal several interesting instances of resonance phenomena in the high-tension transformer circuits. View full abstract»

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  • The Sphere Gap as a Means of Measuring High Voltage

    Publication Year: 1914 , Page(s): 923 - 949
    Cited by:  Papers (1)
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    A gap method of measuring high voltage is desirable in certain tests because a gap measures the maximum point of the voltage wave. The needle gap is unreliable, and is subject to large corrections due to humidity, etc. The sphere gap is free from complicated corrections and the curve is subject to calculation. Wherever voltage is measured by a gap, correction must be made for air density??that is, altitude or barometric pressure, and temperature. The laws for this correction have been deduced for the sphere gap, from tests, over an air density range equivalent to that from sea level to 18,000 ft. elevation. An equation is given for calculating sphere spark-over curves for various spacings, radii, air density, etc. Standard measured curves for convenient sizes of spheres at sea level are given for practical use, as well as a table for applying these curves to any altitude. The altitude correction may be made very accurately to the standard curve, either by applying the calculated correction constant or by applying the correction factor given in the tables. The complete standard curves should not be calculated when reliable measured curves are available. The effects of high frequency and impulse voltages are discussed. In making measurements certain precautions are necessary for accuracy, as well as for protection of apparatus. These precautions are discussed and test results are given. View full abstract»

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  • Concatenated Induction Motors for Rolling Mill Drive

    Publication Year: 1914 , Page(s): 899 - 921
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    The paper describes a six-speed concatenated induction motor set for driving the finishing rolls of a 12-stand continuous mill. Analysis of the conditions in this mill showed that the use of a low-pressure turbine would lead to the waste of a large amount of exhaust steam and that the alternating-current turbine plant which was in operation had ample reserve capacity for driving the mill. The large number of speeds required suggested the use of a direct-current motor, but as this required a motor-generator set it was found to be more expensive than the concatenated motor. An induction motor operating with a speed regulating set was also considered, but its disadvantages lay in the fact that a commutating motor or synchronous converter would be required, the performance of which at the frequency employed was questionable. The concatenated set installed consists of a double-wound main motor and single-wound secondary motor, both stators mounted on a common bed-plate and both rotors on a common shaft. The larger motor has both a 14- and 16-pole stator winding and the secondary motor has its winding arranged for four- and eight-pole connections. The control system is described in detail; its operation is very simple, so that no regular attendant is needed. The motor has six definite speeds and two additional resistance speeds, and while the control is somewhat complicated it has been made so nearly fool-proof as to make a special attendant unnecessary. View full abstract»

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  • Methods of Keeping Down Peaks on Power Purchased on a Peak Basis

    Publication Year: 1914 , Page(s): 887 - 898
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    The author mentions two general ways of reducing peaks, the first being to furnish the peak power from a separate source such as a local steam turbine, and the second to store some of the power furnished by the power company, which is given up later when the peak demand comes on. In the case of the plant described by the author a mixed pressure turbine was installed to take the peaks, this being selected on account of available exhaust steam from pumps, air compressors, etc. The turbine is direct-connected to two direct-current generators mounted on a common bed-plate. The first plan tried was to use a motor-driven rheostat operated with clutches which in turn were operated by solenoids energized by current controlled by a contact-making ammeter. After the installation of a maximum demand meter which integrates the one-minute peaks, the rheostat control was found to be too slow and a special peak-taking device was then installed. This device consists of a rod carrying points which successively make contact with mercury cups and which is operated by the moving element of the graphic meter. These mercury contacts close relay circuits which operate to short-circuit sections of resistance in the field rheostat of the turbo-generator, raising its voltage, and also cut in sections of resistance in the field rheostat of the motor-generator set, weakening its field and thus reducing its load. View full abstract»

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  • Direct-Current Motors for Coal and Ore Bridges

    Publication Year: 1914 , Page(s): 873 - 886
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    This paper gives a brief description of the mechanical arrangement of a coal bridge. The bridge consists essentially of a trolley car with hoisting mechanism for a self-filling bucket. A series-wound motor is recommended for driving the trolley car; and the proper method of gearing the motor for the most economical results is discussed. A series-wound motor is recommended for a low-speed hoist and a shunt-wound motor for a high-speed hoist. The relative merits of the two methods of winding the motor are considered. View full abstract»

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  • The Electrically Driven Gyroscope in Marine Work

    Publication Year: 1914 , Page(s): 857 - 872
    Cited by:  Papers (1)
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    The gyroscope when continuously driven by electric power may be used for various purposes, many of its applications having especial value in marine work. Small gyroscopes are used to establish base lines for the measurement or control of angular motion. The gyro-compass makes use of the earth's daily rotation and consequent changing direction of gravity to secure a directive force a hundredfold greater and more accurate than that of the magnetic compass. A general description is given of the gyro-compass as adopted by the United States Navy for use on all the battleships and submarine vessels. Many electrical and mechanical devices have been developed to perform the various functions whereby an instrument of great precision has been secured. Large gyroscopes are made which are capable of counteracting enormous wave forces and completely stabilizing any ship against rolling in the heaviest seas. View full abstract»

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  • Electric Heating as Applied to Marine Service

    Publication Year: 1914 , Page(s): 839 - 855
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    Electricity is being adopted to a great extent for space heating in marine work because of the simplicity and low cost of installation, saving in weight, freedom from leaks, noises and disagreeable odors as compared to steam heat, availability for heating of individual rooms, ability of placing heaters where most efficient, portability so that storerooms and other seldom-used spaces may be readily heated when desired, ease of regulation so that individual staterooms, etc., can be maintained at any desired temperature without affecting the whole system. A comparison of convector and radiant heaters is given, the proper use of each type is shown, and the conclusion drawn that for space heating on shipboard with metal decks and bulkheads, the convector heater is most efficient. Curves are given showing results obtained on tests to determine the best type of heater for shipboard, and desirable features of heater are indicated. With low cost of electricity on shipboard, electric heating compares favorably in cost of maintenance with steam heating. It interferes very little with the lighting load, thus increasing the load factor, and seldom requires extra generator capacity. View full abstract»

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  • The Evolution of the Institute and of its Members

    Publication Year: 1914 , Page(s): 819 - 838
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  • Delta and Y Connections for Railway Transmission and Distribution

    Publication Year: 1914 , Page(s): 807 - 817
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    Transformer connections under the following three conditions are discussed: The railway (1) purchases power; (2) builds and operates the generating and transmission systems; (3) purchases power and in addition builds and operates a secondary transmission system. The choice between delta and Y connection is frequently determined by purely economic considerations. However, it is common practise to use the delta connection on both the high-and low-tension sides of transformers, except in the case of six-phase converters, where the diametrical connection on the low-tension side is the rule. Synchronous converter substations employing two machines in series for high-voltage d-c. railways, are frequently operated from single banks of transformers, which have double windings on the low-tension sides. Methods of starting have little effect upon transformer connections except in the case of six-phase converters. Transformer connections are seldom important electrically in single-phase and three-phase railway systems. A secondary distribution system may at first be delta-connected and later changed over to Y connection to obtain better voltage regulation. View full abstract»

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  • Relative Merits of Y and Delta Connection for Alternators

    Publication Year: 1914 , Page(s): 803 - 806
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    The main advantages obtained with the Y connection are as follows: (1) It is possible to bring out a lead from the neutral point of the winding, which is useful for various purposes. (2) The cost is less than with the delta connection, requiring approximately 58 per cent of the turns. (3) It is not possible for circulating currents of triple frequency to flow in the windings. The delta connection does not appear to have any advantages except as a convenience in design for certain voltages. When used, proper precautions must be exercised in the design to eliminate excessive circulating currents. View full abstract»

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  • Experience of the Pacific Gas and Electric Co. with the Grounded Neutral

    Publication Year: 1914 , Page(s): 767 - 802
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    The paper gives an outline of the distributing system of the Pacific Gas and Electric Company of California which operates at 60 kv., the transformers being Y-connected, with the neutrals solidly grounded. The company considers the grounded neutral system has a number of important advantages with regard to the transformers, the transmission lines, and operation. The fewer turns of larger capacity of the Y-connected transformers and the fixed lower average voltage to ground greatly increase their reliability. The maximum voltage on the line insulators with the grounded neutral is never more than 57.7 per cent of the line voltage, and it is possible to maintain polyphase service at a substation on a branch line with only two wires in case one wire should be cut out. This cannot be done on a delta system unless one phase of the system be grounded, which is very undesirable. With a grounded neutral, a wire down is instantly detected and power must be shut off. In a delta-connected system an arcing ground is often followed by surges which break down the insulation at other points, the cause of this disturbance being the oscillatory character of the arc. In the grounded Y system no such disturbances occur, as the frequency of an arc to ground is the same as that of the system and any damage is confined to the point of failure. View full abstract»

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  • A Study of Some Three-Phase Systems

    Publication Year: 1914 , Page(s): 753 - 766
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    The star-star, delta-delta, delta-star and star-delta connections are taken up in order and their individual peculiarities and characteristics, precautions that must be taken in operation to avoid trouble, and where and when the system may be grounded with best results, are discussed. The question of delta-delta vs. delta-star is considered: (1) For moderate voltages the delta-delta system has the advantage on account of its greater flexibility. (2) For high voltages the delta-star connection is preferable, chiefly on account of its greater strength and lower cost. There is a probability that a delta-star bank of transformers will cause less disturbance in switching than one that is delta-delta connected. (3) There are much greater possibilities of development in transformers designed for delta-star connection than for any other. (4) Past and present practise upholds the use of the delta-star connection in preference to the delta-delta for high-voltage transmission. View full abstract»

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  • Influence of Transformer Connections on Operation

    Publication Year: 1914 , Page(s): 735 - 752
    Cited by:  Papers (4)
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    In this paper the relative advantages and disadvantages in operation of the more important three-phase transformer connections are discussed. Three conditions of operation are given: First, normal; second, operation of a bank with one phase disabled; third, effect of line grounds on operation. The paper is not complete, particularly in that high-frequency or switching phenomena are not discussed. Its major purpose is to give a fairly adequate presentation of insulation stresses at relatively low frequencies to which transformers are subject in either normal or abnormal conditions of operation. These frequencies include the fundamental or generated frequency and its harmonics and the natural frequency of the system. The behavior of three-phase auto-transformers under the various conditions of operation given above is also analyzed. View full abstract»

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  • Harmonic Voltages and Currents in Y- and Delta-Connected Transformers

    Publication Year: 1914 , Page(s): 723 - 733
    Cited by:  Papers (3)
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    The paper reviews the conditions under which triple harmonic voltages and currents are produced in Y- and delta-connected transformers. These voltages are produced by hysteresis in the core. In a single-phase transformer, increase of series resistance tends to suppress the current harmonic and produce the voltage harmonic. In three-phase transformers, a Y connection suppresses the current harmonic and allows the full flux and voltage harmonics to appear. Delta connection provides a closed path for the current harmonic, and suppresses the triple voltage. A case is cited where a Y-connected auto-transformer was used to step up from 6600 to 12,000 volts at a substation. The neutral was not grounded, and trouble resulted due to partial resonance at triple frequency between line capacity and transformer reactance. The paper shows that, although not generally recognized, a triple component can exist in the line-to-line e.m.f. wave of a three-phase system. This is possible in a case where a two-to-three-phase transformation is used, and when the e.m.f. wave of the two-phase generator contains a triple harmonic. Vector diagrams and curves are given illustrating this possible effect. View full abstract»

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  • Inherent Voltage Relations in Y and Delta Connections

    Publication Year: 1914 , Page(s): 711 - 721
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    The paper gives the results of experiments made with a miniature simple transmission system to demonstrate the inherent voltage relations with different combinations of Y and delta connections. The experimental system consisted of a 7.5-kv-a. revolving field generator, with coil terminals which could be connected either Y or delta, and two banks of transformers each composed of three shell-type 3-kv-a. units. All inductive and capacity effects in the transmission line were eliminated. The tests were made under constant conditions, with non-inductive load. The authors give the results of four groups of tests, on four different systems of connections, pointing out the advantages and disadvantages of the several systems. In each case tests were made without load, with balanced load, and with load on one phase only, for various conditions of grounding. Typical voltage diagrams are given, to show what happens under various conditions of load. The authors discuss certain cases where the use of auto-transformers is advantageous, and the effects of different ways of connecting them. View full abstract»

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  • Experiences with Line Transformers

    Publication Year: 1914 , Page(s): 685 - 710
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    This paper presents an analysis of the transformer troubles for one year on a system having nearly 15,000 transformers installed. This analysis indicates that about 50 per cent of the troubles traceable to the transformer can be eliminated, with no great expense, by some slight changes in the construction details and some improvements in operating methods. Reference is made to the Standard Specifications for Line Transformers issued by the Bureau of Standards. An experiment on 1600 transformers with the connection board removed or submerged proved that the connection board above oil was responsible for about 60 per cent of the transformer troubles due to lightning. Curves showing the record of burnouts of four different makes of transformers are used as a basis for a discussion of the effect of the value placed on continuous service in the selection of transformers. The results of experiment with improved lightning protection are given, showing how the troubles were reduced by two-thirds. By taking advantage of the results of the two extended experiments, itshould be possible to reduce the troubles due to lightning to about 10 per cent or 20 per cent of the troubles heretofore experienced. View full abstract»

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  • Effect of Electrolysis on the Compressive Strength of Cement and Concrete

    Publication Year: 1914 , Page(s): 673 - 684
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    A paper on ``The Electrolytic Corrosion of Reinforced Concrete'', by C.E. Magnusson and G. H. Smith, was read before the A. I. E. E. June 30, 1911, and, as stated in that paper, the results could not be pronounced entirely conclusive, as the duration of the experiments was only 30 days. In the present paper a similar series of experiments is described by the authors in which the tests were continued for several months. The paper gives in tabular form the results of a large number of experiments and the conclusions corroborate the results reported in the former paper. For the current density covered by the experiments, the current was found to produce no change in the compressive strength of concrete cubes, from which it is deduced that the failures of reinforced concrete due to electrolysis are due entirely to the forces produced by the increase of volume when iron is changed into iron oxide, and not by any direct action of the current upon the concrete. View full abstract»

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  • The Future of Electric Heating and Cooking in Marine Service

    Publication Year: 1914 , Page(s): 659 - 672
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    Indications of the future point to electric motor-driven propulsion and abandonment of coalburning boilers. Electric cooking and heating is in line with this development and the source of heat for cooking and heating will be confined to the boiler room. The future of electric cooking apparatus is assured by the progress already made in the U. S. Navy in adopting electric equipment. Detailed report is given of trial trip of U. S. S. Texas, which depends almost entirely upon electricity for cooking. Consumption of 1.25 kwhr. per person per meal is indicated. Load factor was 50 per cent. Electric ranges and bake ovens effect considerable saving in weight and space and release cooks from being `` firemen '' to devote their time and effort to good cooking. Electric cooking finds greatest advantages in high temperature cooking. Electric heating on shipboard does away with the disadvantages of steam piping and gives individual and local regulation and provides, where desired, glowing heat without fire. Other accessories are the electric flatiron, the soldering iron and therapeutic devices. View full abstract»

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  • Electricity the Future Power for Steering Vessels

    Publication Year: 1914 , Page(s): 619 - 657
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    Electrical development in the marine field has been confined in a large measure to the navy, and the best experience with electric steering gears has been obtained from navy installations. Up to the present time steam has been the universal power for operating steering gears, but certain disadvantages are in-herent in this system which can be overcome by the electric drive, and additional advantages obtained. The history of electric gears shows that many different schemes have been tried and proved failures owing to faulty designs and imperfectly developed apparatus. At present several different systems are in successful operation. To obtain full benefit of the advantages possible from an electric drive, much depends on the selection of apparatus with characteristics best suited to the work. The problem of electric drive is largely one of control. The calculations for rudder and motor horse powers must be carefully made, with the proper assumptions for the conditions presented. Several installations in the navy have shown excellent results; in the case of the battleship Texas the data obtained show preliminary calculations were quite accurate. Results obtained seem to justify the prediction that electric steering gears will be used quite generally in the future. View full abstract»

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  • Theory of the Corona

    Publication Year: 1914 , Page(s): 589 - 617
    Cited by:  Papers (3)
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    The theory of the corona developed in this paper explains the coronal discharge by the application of the known laws of the discharge of electricity through gases. The experiments of Dr. Whitehead and Mr. F. W. Peek and others have shown that the surface gradient Xs at the surface of a smooth wire necessary to start the corona increases very greatly as the radius of the wire decreases. As an illustration of this increase it is found that the coronal gradient Xs at the surface of a wire of 0.5 cm. radius is 46,000 volts per cm., while a gradient of 97,000 volts per cm. is required for a wire of 0.02 cm. radius. The phenomenon is due to ionization by impact. The ions no move in toward the wire from the place at which they cross a region where the gradient is X0 = 26,600 volts per cm. up to the wire. They produce other ions, and n ions arrive at the wire. The condition for the corona is that n shall be a constant. If ?? = the number of ions that one ion produces in a cm., then fb ?? dx n = no e a The ?? is a function of X at every point. This function is expressed in terms of x. It is introduced into the above equation, and on integration the equation for the corona is obtained. The equation also contains a term for the density of the air. View full abstract»

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  • A Milliampere Current Transformer

    Publication Year: 1914 , Page(s): 571 - 588
    Cited by:  Papers (2)
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    (1) It is pointed out that by the use of a current transformer having a primary to secondary current ratio of the order of 1 to 100, oscillograms can be obtained of the charging current of a single high-tension insulator or of a few feet of high-tension transmission line; that is, oscillograms of currents of the order of 0.1 to 0.5 milliampere may be obtained. (2) The drawings and specification are given for a transformer for this purpose. (3) The transformer relations are discussed; the methods of determining the transformer constants are outlined, and the performance of transformers constructed in accordance with the specifications is determined. (4) A series of oscillograms is given to illustrate some of the applications of the transformer, such as to the study of corona, high-tension insulators, and leakage currents in evacuated lamps. View full abstract»

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  • Some Simple Examples of Transmission Line Surges

    Publication Year: 1914 , Page(s): 545 - 569
    Cited by:  Papers (2)
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    The paper treats of the true wave phenomena which take place on a transmission line when switches are opened and closed or when a circuit breaker operates. These phenomena are practically the same in alternating- and direct-current systems for transmission lines up to say 150 or 200 mi. (240 or 320 km.) in length, and therefore the surges which are described in the paper are the surges which take place when a steady voltage is connected to the line or when the line is disconnected with a steady current flowing in it. The details of line surging which takes place under such conditions are most easily described in terms of what may be called the ``ribbon wave'', and the first part of the paper is devoted to a discussion of the ribbon wave. Then a number of practical examples are described in detail. View full abstract»

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  • Some Investigations on Lightning Protection for Buildings

    Publication Year: 1914 , Page(s): 519 - 544
    Cited by:  Papers (3)
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    A description is given of investigations conducted for a large manufacturer of explosives to determine upon a suitable system of lightning protection for buildings containing explosives. The work is divided into the following sections: (1) An analysis by oscillograph of the secondary currents induced by actual lightning discharges in vertical earthed conductors, the results seeming to indicate that such currents are non-oscillatory and aperiodic, though occurring in either a negative or positive direction. An attempt is made to explain the phenomena generally attributed to high, frequency oscillations by the existence of unidirectional waves of almost vertical front. (2) An investigation of the primary effects of a 20-in. spark in air, having the same essential characteristics as those attributed to lightning, when applied to a model protective system consisting of isolated vertical conductors surrounding a small building. (3) An investigation of the secondary effects produced under the above conditions, which are considered to be static inductive rather than dynamic inductive. A brief description is given of a general protective system recommended for explosives buildings. View full abstract»

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