Showing papers in "Journal of the Institution of Electrical Engineers in 1927"
27 citations
TL;DR: The circuit arrangements devised by Boucherot to give a constant-current supply from a constantvoltage supply are briefly described, and it is then shown that they may be regarded as simple examples of a more general property of all electric filters as discussed by the authors.
Abstract: The circuit arrangements devised by Boucherot to give a constant-current supply from a constant-voltage supply are briefly described, and it is then shown that they may be regarded as simple examples of a more general property of all electric filters
20 citations
TL;DR: In this article, the effect of attenuation due to the collision of electrons with molecules is especially stressed and a novel theory of skip distance is put forward which has the merit of agreeing closely with the observed results of Heising, Schelleng and Southworth.
Abstract: This paper deals with the state of the short-wave practice and theory, and describes experiments made by the author to elucidate short-wave transmission phenomena, and certain theoretical developments based on these experiments. In the first Section the aerial transmission characteristics are dealt with; in particular the vertical polar diagrams of transmission are computed, taking account of the earth's resistivity, and it is shown that these are all characterized by the absence of horizontal radiation. It is also shown that the intensity of the low-angle transmission is increased by raising the transmitting aerial. In the second Section the results of a series of experiments in which a short-wave radio direction-finder is used are described, and the conclusion is arrived at that in long-distance transmission the ray trajectory has a shallow angle of elevation 15°, and follows the great-circle path. In the third Section the results of a series of long-distance transmission tests is given. Waves between 25 and 10 m were used, and experiments were made which indicated the superiority of a raised doublet over one at the ground-level. In the last Section the general theory of ionic refraction is discussed in the light of these and other experimental results. The effect of attenuation due to the collision of electrons with molecules is especially stressed and a novel theory of the skip distance is put forward which has the merit of agreeing closely with the observed results of Heising, Schelleng and Southworth.
11 citations
9 citations
TL;DR: In this article, the stability, voltage control, and power limits of large alternating-current systems and synchronous machines were investigated. But the authors only considered the case of large-scale systems.
Abstract: The paper deals with the stability, voltage control, and power limits of electric- power systems and machines?more particularly, large alternating-current systems. The subject is dealt with in the following sequence :? Definition of stability. Stability and power limits of simple circuits. Larger power lines. Artificial stability of power lines. Natural stability and power limits of alternators and synchronous machines. Short-circuits and transient stability of alternators. Internal reserve of excitation of synchronous machines. Artificial stability of alternators. Stability of exciters. Types of electric power supply systems. Feeders and transmission lines and their voltage control. The conclusions reached are that synchronous machines can be made sufficiently stable for all the usual purposes of power supply, and that the power limit and voltage regulation of transmission circuits depend principally on their series reactance.
7 citations
TL;DR: In this paper, the authors discuss the capacities, the mutual actions and the field in the neighbourhood of two electrified spherical conductors, showing that when their potentials or charges are of like sign, the force between them may be attractive or repulsive, depending on the ratio of the potential or charges or the charges.
Abstract: In continuation of his previous paper on the spherical condenser † the author discusses the capacities, the mutual actions and the field in the neighbourhood of two electrified spherical conductors. After a brief introductory statement of this historical problem an attempt is made to solve it by elementary theory. The magnitudes of the errors introduced by this method are pointed out. Accurate formulae are then obtained by the method described in the preceding paper. These formulae enable the capacity coefficients to be computed in all cases to any required degree of accuracy without difficulty. A few simplified formulae which will be useful in practice are also given. The discussion of the mutual actions between the spheres shows that when their potentials or charges are of like sign the force between them may be attractive or repulsive, depending on the ratio of the potentials or the charges. In this case there are always two ratios of the charges and of the potentials which make the mutual force zero. Methods of computing the forces in other cases are given. Simple formulae are found for calculating the potential gradients at the points on the spheres where the line joining their centres cuts their surfaces. This tells us whether the charge on the spheres is all positive or all negative or partly positive and partly negative. In the Appendix a few more accurate but more elaborate formulae are given.
7 citations
TL;DR: The paper closes with a description of the methods adopted in the Post Office for measuring traffic and traffic overflows, and of the use made of these measurements.
Abstract: After an introduction defining the scope of trunking, the ideas “traffic unit” and “grade of service” are investigated in some detail. The history of trunking is touched on briefly, this Section terminating with a description of the means provided in modern exchanges for connecting one rank of switches with another. The traffic-carrying capacity of switches under the “ full availability” condition leads to a consideration of the possible methods of trunking when the availability is “limited.” The particular method called “grading” is described in detail and the traffic capacity of various grading arrangements is investigated. The effect of changes in the distribution of traffic is next considered, and then information is collected regarding the design curves used by the Post Office. The paper closes with a description of the methods adopted in the Post Office for measuring traffic and traffic overflows, and of the use made of these measurements.
6 citations
TL;DR: In this article, a comparison between two methods of calibrating a Rayleigh disc is made, namely, by means of low-frequency alternating air currents and by calculation based on the theoretical formula.
Abstract: In Part 1, possible methods of calibrating a Rayleigh disc are discussed, and details are given of a comparison between two of these, namely, by means of low-frequency alternating air currents and by calculation based on the theoretical formula. In consequence of agreement found between these, the latter has been adopted as the most convenient practical method of calibration. In Part 2, comparisons are made between Rayleigh discs of different sizes and compositions, both in spherical sound waves and in a closed resonating tube. The influence of internal resonances of mica discs on velocity measurement is investigated. In Part 3, comment is made on practical considerations affecting acoustic measurements by means of a Rayleigh disc.
4 citations
TL;DR: In this article, the authors describe null methods of measuring the ratio and phase displacement of two alternating voltages, which are particularly applicable to high voltages and are discussed in connection with the testing of power transformers and potential transformers.
Abstract: The paper describes null methods of measuring the ratio and phase displacement of two alternating voltages. The methods are particularly applicable to high voltages and are discussed in connection with the testing of power transformers and potential transformers. An important feature is the use of a capacitance potential divider in place of the resistance typeof potential divider which has hitherto been used. Capacitance potential dividers possess considerable advantages over those of the resistance type from the point of view of simplicity and low cost of equipment and ease of operation, while the accuracy can be made as high as is desired. The maximum voltage at which the use of resistance potential dividers is practicable is of the order of 30 kV, whereas there is practically no limit to the voltage at which capacitance potential dividers can be used. The theory of a method of measuring the ratio and phase displacement of transformers is given and the operation of the method is illustrated by a test on a 66 000-volt potential transformer. Suggestions are made for the developing of an apparatus for routine industrial testing and it is pointed out that a robust construction and adequate safety to the operator could be secured while retaining ample accuracy for commercial purposes. The use of a tapping on the secondary winding of a high-voltage testing transformer for the purpose of operating a wattmeter or voltmeter is considered, anda method of determining the ratio and phase displacement of the full and fractional voltages is given. The testing of high-voltage potential dividers is also briefly considered.
3 citations
TL;DR: In this paper, the use of series condensers for the extension of the range of electrostatic voltmeters for extra-high-voltage measurements is dealt with, the conditions necessary for the attainment of reasonable accuracy being considered.
Abstract: The writing of this paper has been prompted by the large amount of valuable material which has been produced during the last few years, but little of which has been brought into such a form as to make it available to the designer of electrical measuring instruments. By a process of elimination, the operating principles employed are gradually becoming less in number. For example, the use of the hot-wire principle is now almost confined to radio-frequency measurements, and the prophecy is hazarded that for the measurement of current and voltage at ordinary frequencies the electro-dynamic and induction principles will, before long, give place to the moving-iron principle. A useful feature possessed by the moving-iron type of meter is the wide latitude which is possible as regards the opening out or closing in of the scale divisions to suit the purpose for which it is required. The moving-iron instrument is investigated, from what is thought to be a new standpoint, and a form of ? precision? moving-iron ammeter and voltmeter, with an electrical accuracy of about 0.1 per cent and suitable for use indiscriminately with alternating current and direct current, is described. The use of series condensers for the extension of the range of electrostatic voltmeters for extra-high-voltage measurements is dealt with, the conditions necessary for the attainment of reasonable accuracy being considered. The use and limitations of thermo-expansion (hot-wire) ammeters for radio-frequency current measurements are considered, and a current transformer suitable for such measurements up to 1 000 amperes is described. It is shown that special considerations are involved in the measurement of rectified current. Some recent developments in the field of graphic instruments are dealt with, particularly as regards the ?relay? pattern which has proved to be valuable for traction and many other special purposes. A method of ensuring constant frequency on a supply system is considered, together with the advantages which accrue, particularly as regards ease of interlinking, and the possibility of driving recorders, time switches, etc., bymeans of a simple and compact self-starting synchronous motor. The design of current transformers is dealt with in detail, including the use of some new materials for the core, permeability and core-loss curves being given. The design of a bar (bushing) current transformer for lowcurrents as well as of a precision type of current transformer is described. The latter is suitable for use with sub-standard measuring instruments, and has a ratio error of less than 0.1 per cent and a phase displacement of less than 5 minutes. The desirability of connecting a protective resistance in series with voltage-transformer fuses is emphasized, and it is shown that such a resistance, if properly designed, need not adversely affect the characteristics of the transformer. The capacity of meters, shunts, current transformers, etc., to withstand heavy short-circuit currents is considered, and safe limiting values are deduced.
3 citations
TL;DR: The controversy as to the calculation of sheath circulating-current losses is referred to, and single-phase tests are quoted to show which formulae agree best with actual measurements as discussed by the authors.
Abstract: The controversy as to the calculation of sheath circulating-current losses is referred to, and single-phase tests are quoted to show which formulae agree best with actual measurements. Formulae for the circulating currents in three single-core cables with either horizontal or delta spacing are developed and experimental results are given to show how these agree with the values calculated from the formulas.
TL;DR: In this paper, it was shown that for close or practical spacing the formulae published in the I.E. Journal give a result too low and also that the term log[(1−K)/K] should be changed to log (1/K)
Abstract: Formulae for calculating the eddy-current loss in the bonded sheaths of single-conductor cables have been published in the I.E.E. Journal. These contain a term log [(1−K)/K] instead of the usual term log (1/K) used by most authors in formulae for this purpose, namely those published in the Electric Journal. These two terms are caused by using different limits in integrating the conductor flux, thereby producing quite a difference in the results obtained by the two methods.The present author has carried out an investigation by working out a practical example, using an independent method, with a view to determining which formula is correct. The results of this investigation show that for close or practical spacing the formulae published in the I.E.E. Journal give a result too low and also that the term log[(1−K)/K] should be changed to log (1/K)
TL;DR: In this paper, the authors proposed a system suitable for adoption as a standard and to consider how far existing systems may gradually be brought into line with it by considering the possibility of standardization.
Abstract: It is believed that the future will bring a rapid growth of load and that this makes the present a suitable moment to analyse city distribution methods, settle a policy of development and consider the possibility of standardizationThe main object of the paper is, therefore, to design a system suitable for adoption as a standard and to consider how far existing systems may gradually be brought into line with itThe various sections of a city distribution system are reviewed in sequence from the consumer to the main transmission system (or local power station) under the following headings, particular attention being given to the design of a system lay-out which facilitates expansion to deal with growing load:—(a) The type and voltage of current to be delivered to the consumers(b) The general lay-out of the low-voltage distribution system(c) The general lay-out of the high-voltage distribution system for feeding the low-voltage system through transforming centres(d) The voltage to be adopted for supplying the transforming centres from the main substations on the transmission system(e) The size and spacing of transforming centresIt is believed that the future will bring a rapid growth of load and that this makes the present a suitable moment to analyse city distribution methods, settle a policy of development and consider the possibility of standardizationThe main object of the paper is, therefore, to design a system suitable for adoption as a standard and to consider how far existing systems may gradually be brought into line with itThe various sections of a city distribution system are reviewed in sequence from the consumer to the main transmission system (or local power station) under the following headings, particular attention being given to the design of a system lay-out which facilitates expansion to deal with growing load:—(a) The type and voltage of current to be delivered to the consumers(b) The general lay-out of the low-voltage distribution system(c) The general lay-out of the high-voltage distribution system for feeding the low-voltage system through transforming centres(d) The voltage to be adopted for supplying the transforming centres from the main substations on the transmission system(e) The size and spacing of transforming centresThe desirable characteristics are then summarized so as to outline the proposed “standard” system Suggested standards are also laid down for the capacity of the individual parts in areas of different type and load densityThe above is followed by three short studies, based on the detailed calculations necessitated by the main investigation These deal with (i) the relative costs of the different elements of the distribution system, (ii) the effect of load density on the cost of distribution, and (iii) the relative costs of direct-current and alternating-current distributionIn conclusion, some consideration is given to the general question of bringing existing city distribution systems into line with the proposed standard system with the object of attaining, ultimately, complete standardization of distribution throughout the country
TL;DR: In this article, the authors deal with parasitic current set up in an armature bar on reversal of the current by the commutator, and show how the additional loss in the bar due to this current can be determined as a fraction of the loss due to the effective current.
Abstract: The paper deals with parasitic current set up in an armature bar on reversal of the current by the commutator, and shows how the additional loss in the bar due to this current can be determined as a fraction of the loss due to the effective current.
TL;DR: In this article, the authors give a few historical facts leading to the adoption by the District Railway of 600 volts direct current with the insulated return, and makes reference to the starting up of the Tube lines.
Abstract: The paper gives a few historical facts leading to the adoption by the District Railway of 600 volts direct current with the insulated return, and makes reference to thestarting up of the Tube lines. It also deals with:- Some results in working the insulated-return system. Conductor rails; material used, section, conductivity, loss of weight, anchoring, and data with regard to the painting of rails. Types of insulators used and data with regard to cleaning and insulation. Injurious effect of electric burns on track rails. High-tension cables. Maintenance of track equipment, including methods adopted forclearing ice or snow from conductor rails. Operating arrangements for removing and restoring current. Some particulars are also given of certain special instruments used by the Underground Railways. The conclusions reached by these Railways are set out at the end of the paper.
TL;DR: In this article, a description of the 60,000-volt underground cable network which has been successfully operated in the Paris district by the Union d'Electricite for the past four years is given.
Abstract: This paper contains a description of the 60,000-volt underground cable network which has been successfully operated in the Paris district by the Union d'Electricite for the past four years. The reasons why single-core cables were adopted for the distribution system are explained, and a number of details are given in regard to the construction of the cables, the method of laying, and the operating conditions, both electrical and thermal.
TL;DR: In this article, the design and operation of a high-power valve transmitter installed at Rugby radio station is discussed. And the results of recent signal measurements and a schedule of readings under present normal working conditions are given.
Abstract: The paper deals with certain specific details of design and operation of the high-power valve transmitter installed at Rugby radio station, and is divided into six parts. Part I discusses the arrangement of the coupled aerial circuit of a valve transmitter, and shows that certain circuits have considerable advantages over others in respect of the elimination of harmonics. Part II indicates the considerations which govern the choice of the electrical proportions of the intermediate and aerial circuits, simple formulae being given for the calculation of the different quantities involved. Part III deals with the question of the design of large inductance coils, and compares measured values of the high-frequency resistance of certain coils with the calculated values. Part IV contains some notes on valve-circuit design, compares two conditions of operation of a valve transmitter and gives an analysis of the present operating condition at Rugby. The comparative operation of valves in low- and high-power transmitters is also discussed. Part V gives oscillograms of the shape of signals emitted when using different keying arrangements, and indicates the improvement obtained in certain cases. The transients due to keying are discussed briefly also. Part VI gives the results of recent signal measurements and a schedule of readings under present normal working conditions.
TL;DR: The rating of traction motors is discussed, and it is shown that the one-hour rating has no significance in connection with modern motors, and should be dropped, in as much as it tends to interfere with rational development.
Abstract: The rating of traction motors is first discussed, and it is shown that the one-hour rating has no significance in connection with modern motors, and should be dropped, inas-much as it tends to interfere with rational development. The heating of the motors is then analysed, and methods for estimating it in a given service are described. Finally, service tests are discussed, with their relation to certain stand-tests based on the given service.
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TL;DR: In this article, the authors analyse some of the various starting arrangements used with single-phase induction motors and propose to use electric starting devices only for fractional horse-power machines.
Abstract: The object of this paper is to analyse some of the various starting arrangements used with single-phase induction motors. As is well known, these machines have inherently no torque at standstill but require special devices to produce this torque by altering the motors during the starting period into unsymmetrical polyphase induction motors. It is proposed to deal only with electric starting devices, which have found an extensive commercial application for motors from about 1 to 100 h. p. Mechanical means of bringing single-phase induction motors such as pony motors, etc., up to speed, will not be considered in this paper. Inductive devices of either the external or the internal type are practically confined in their application to fractional horse-power machines and therefore will only be mentioned here for the sake of completeness.
TL;DR: In this article, the main properties of silica as an envelope for high-power valves are enumerated and the valves are divided into two main classes depending on whether the anode heat is removed by radiation or by the use of a cooling fluid.
Abstract: The paper discusses the construction for Naval purposes of wireless transmitting valves with silica envelopes. The main properties of silica as an envelope for high-power valves are enumerated and the valves are divided into two main classes depending on whether the anode heat is removed by radiation or by the use of a cooling fluid.A description is given of the electrode seals which have been developed to carry currents up to 100 amperes.The various types of valves and the methods of construction, evacuation and repair are described.The dimensions of standardized valves and the methods adopted for removing the heat generated in the various types of valve anodes are dealt with.The operating conditions for transmitting circuits and the methods of packing for transport are briefly referred to.
TL;DR: In this article, it appears that it is the practice to state the volume of air displaced per minute by a ceiling fan without any reference to the conditions under which the measurements are made.
Abstract: It appears to be the practice to state the volume of air displaced per minute by a ceiling fan without any reference to the conditions under which the measurements are made. The tests detailed in this paper were undertaken to determine the influence upon the measured volume of air of: (a) Distance of plane of observation below fan blades. (b) Position of fan in, and size of, room. (c) Height of fan above floor. (d) Distance between fan and ceiling. (e) Room temperature. (f) Speed of fan. Recommendations are made relating to the conditions under which air velocities should be observed.
TL;DR: The early experiences with oil as an insulating and cooling medium are first briefly reviewed, showing the recognition of the several essential characteristics as mentioned in this paper, and the fundamental attack which has been made upon the sludge problem in Great Britain, and outlines the organized research inaugurated by the Institution and continued by the Electrical Research Association.
Abstract: The subject ?Results of Research on Insulating Oils? having been placed on the agenda for the meeting in June 1925 of the Paris Conference on Large High-Tension Electric Supply Systems, this paper was prepared as a contribution from the British delegation. The early experiences with oil as an insulating and cooling medium are first briefly reviewed, showing the recognition of the several essential characteristics. The paper then shows the fundamental attack which has been made upon the sludge problem in Great Britain, and outlines the organized research inaugurated by the Institution and continued by the Electrical Research Association. The results obtained are briefly reviewed. A Bibliography is attached, and certain Reports of the Electrical Research Association which have been published in the I.E.E. Journal were included as Appendices to the paper when presented to the Paris Conference.
TL;DR: In this paper, the authors describe the Holweck molecular pump and demountable valve types, and some results obtained with installations employing demountably valve types are given, and the possibility of larger-power single units being developed is mentioned.
Abstract: The paper briefly describes the Holweck molecular pump and, in more detail. 10- and 30-kW Holweck demountable type valves. Precautions necessary with demountable valve installations are pointed out. The chief advantages are ability to renew filaments at a cost of a few pence, and ability to carry large overloads. Some results obtained with installations employing demountable valves are given. The possibility of larger-power single units being developed is mentioned, but short-wave work may make it unnecessary to build larger units than those developed. Perfection of details with a view to complete reliability should make for increased application of this type of valve.