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Showing papers in "Transactions of The American Institute of Electrical Engineers in 1918"


Journal Article•DOI•
TL;DR: In this article, a general discussion of unsymmetrical systems of co-planar vectors leads to the conclusion that they may be represented by symmetric systems of the same number of vectors, the number of symmetrical systems required to define the given system being equal to its degrees of freedom.
Abstract: In the introduction a general discussion of unsymmetrical systems of co-planar vectors leads to the conclusion that they may be represented by symmetrical systems of the same number of vectors, the number of symmetrical systems required to define the given system being equal to its degrees of freedom. A few trigonometrical theorems which are to be used in the paper are called to mind. The paper is subdivided into three parts, an abstract of which follows. It is recommended that only that part of Part I up to formula (33) and the portion dealing with star-delta transformations be read before proceeding with Part II. Part I deals with the resolution of unsymmetrical groups of numbers into symmetrical groups. These numbers may represent rotating vectors of systems of operators. A new operator termed the sequence operator is introduced which simplifies the manipulation. Formulas are derived for three-phase circuits. Star-delta transformations for symmetrical co-ordinates are given and expressions for power deduced. A short discussion of harmonics in three-phase systems is given. Part II deals with the practical application of this method to symmetrical rotating machines operating on unsymmetrical circuits. General formulas are derived and such special cases, as the single-phase induction motor, synchronous motor-generator, phase converters of various types, are discussed.

785 citations


Journal Article•DOI•
TL;DR: In this article, a method for calculating the skin effect resistance ratio of a tube, which is a form of conductor to be recommended for high-frequency work, is presented, and a formula is also developed by means of which the asymptote to the curve of the ratio R?/R may be drawn, and thus the magnitude of the skin effects at extremely high frequencies may be obtained.
Abstract: A method is presented for calculating the skin effect resistance ratio of a tube, which is a form of conductor to be recommended for high-frequency work. A formula is also developed by means of which the asymptote to the curve of the ratio R?/R may be drawn, and thus the magnitude of the skin effect at extremely high frequencies may be obtained. The values of the ratio R?/R for tubes of various thicknesses, are plotted in a set of curves (Fig. 3) which may be used for the solution of practical problems. A similar method is described for the calculation of skin effect in a thin strap. Although the calculations cannot be carried out for as high frequencies as the calculation for tube, it indicates a method of coordinating the test results for straps, which have been published. A set of empirical curves for straps is given in Fig. 7, from which approximate values of R?/R for any case may be read.

105 citations


Journal Article•DOI•
TL;DR: In this article, a comparison of calculated and test values (obtained from saturation and synchronous impedance curves) for 138 machines, ranging from high-speed turbine generators to the low-speed engine type, is presented.
Abstract: Part I treats of the calculation and application of the armature self-inductive reactance of synchronous machines. A short, reliable method is given in the form of curves, Figs. 20A, B, C, making the calculation from design sheet data a matter of a few minutes. Table I shows a comparison of calculated and test values (obtained from saturation and synchronous impedance curves) for 138 machines, ranging from high-speed turbine generators to the low-speed engine type. Three points were brought out during the investigation: (1) That in polyphase machines, the armature self-inductive reactance, just as the armature reaction, is a polyphase, not a single-phase phenomenon, and therefore the mutual induction of phases in a three-phase machine increases the effective self-induction of each phase by approximately 50 per cent over the single phase value, while in two-phase machines, in which the mutual induction of phases is zero, the effective self-induction of the phase is the same for two-phase or single-phase operation. (2) That the variation of armature reactance during the cycle, due to salient-pole construction, is practically eliminated in Y-connected, three-phase machines for the reason that the variation, consisting almost entirely of a third harmonic, is cancelled in such machines. This leaves, in effect, a uniform reluctance for the leakage flux emanating from the tooth tips. (3) That in the familiar method of obtaining the armature self-induction from the saturation and synchronous impedance curves (i.e.

43 citations


Journal Article•DOI•
TL;DR: A pole face area in square centimeters is defined as the area of a pole face in square meters as mentioned in this paper.The list of symbols in this article is presented in Section 2.1.
Abstract: List of Symbols A Pole face area in square centimeters

34 citations


Journal Article•DOI•
TL;DR: A critical review of the articles pertaining to this subject, which have appeared in the technical press to date, is given in this paper, where it is pointed out wherein the various expressions which have been proposed differ from one another and to what extent they are consistent.
Abstract: The purpose of this paper is to serve as an introduction to the succeeding comprehensive article by Mr. E. Rosenberg, on the subject of Magnetic Pull in Electric Machines. The Maxwell equation, upon which all of the formulas for unbalanced magnetic pull are based, is first established. A critical review is then given of the articles pertaining to this subject, which have appeared in the technical press to date. It is pointed out wherein the various expressions which have been proposed differ from one another and to what extent they are consistent.

15 citations


Journal Article•DOI•
TL;DR: In this paper, the merits and demerits of each frequency were discussed, and the reasons each one met certain pressing commercial conditions at the time it was brought out, and a discussion of various alternating-current applications which were more or less dependent upon frequency.
Abstract: The various frequencies used in alternating-current work in America are first mentioned, and the primary reasons for their introduction are given. This covers, to a certain extent, the merits and demerits of each frequency as then understood, and the reasons each one met certain pressing commercial conditions at the time it was brought out. This is followed by a discussion of various alternating-current applications which were more or less dependent upon frequency. It is shown that there was an apparent need for two standard frequencies in the region of 60 and 25 cycles, and, further, why 60 and 25 cycles have prevailed. The special fields of application of each one are discussed fully and it is shown why 25 cycles tended to dominate the field. The persistent developments of the designing engineers gradually overcame the limitations in various types of 60-cycle apparatus so that eventually the 60-cycle system in its application approached more and more closely to the 25-cycle and, in the end, has taken the lead. The outcome of the battle of the frequencies was determined far more by the conditions in the operating field than by the exploitation of any particular system by designing engineers. As a consequence, the energies of the engineers were directed exclusively toward overcoming the defects and limitations of the systems and not expended in fighting each other.

13 citations


Journal Article•DOI•
TL;DR: In this paper, the authors discuss the interpretations of the A. I. E. Standardization Rules covering the rating of oil circuit breakers and consider the variable factors which are involved in the selection of circuit breaker for various systems.
Abstract: On account of the variable conditions in systems on which circuit breakers are used, it is impossible to give a simple rule which will cover the selection of circuit breakers for all cases. The authors discuss the interpretations of the A. I. E. E. Standardization Rules covering the rating of oil circuit breakers and consider the variable factors which are involved in the selection of circuit breakers for various systems. A method is suggested whereby short-circuit characteristics of various systems can be used for determining the proper selection of oil circuit breakers for average systems. The method does not apply to very large systems or unusual conditions.

11 citations




Journal Article•DOI•
TL;DR: In this paper, the authors describe the method used at the Electrical Testing Laboratories for measuring the dielectric power losses in 10-foot samples of three-conductor cables with three-phase potential applied to the cable.
Abstract: This paper describes the method used at the Electrical Testing Laboratories for measuring the dielectric power losses in 10-foot samples of three-conductor cables with three-phase potential applied to the cable. The difficulties encountered and the methods employed to overcome them are discussed in considerable detail. Typical results are given in the form of data for two specimens of cable, one having a low power loss in the dielectric and one having a high power loss in the dielectric. The data are also presented in the form of curves. The discussion includes: (a) The theory of excessive internal dielectric loss as accounting for cable failures at local ``hot spots.'' (b) The advantages of plotting data with logarithmic scales. (c) A comparison of results obtained by computation from single-phase measurements with those obtained by direct measurement with three-phase potential. The conclusions drawn are: (a) The power loss in the dielectric in a three-conductor cable under actual three-phase conditions can be readily measured in the laboratory with specimens ten feet long. (b) No special apparatus is necessary for such measurements other than a reflecting high sensitivity wattmeter. (c) Apparently the power loss in the dielectric cannot in all cases be accurately calculated from data obtained in single-phase tests although it is highly probable that for all practical purposes the discrepancy would not be serious.

9 citations





Journal Article•DOI•
TL;DR: In this article, the authors present the results obtained in a recent design of transposition systems for telephone circuits exposed to induction from circuits of other kinds, particularly from three-phase power circuits, and the coordinate arrangements of transpositions in the power circuits.
Abstract: This paper presents the results obtained in a recent design of transposition systems for telephone circuits exposed to induction from circuits of other kinds, particularly from three-phase power circuits, and the coordinate arrangements of transpositions in the power circuits The new arrangements are the result of a systematic investigation of the degree of flexibility which could be obtained in the coordination of telephone transpositions and transpositions in outside disturbing circuits, particularly three-phase power circuits In presenting the results obtained, a discussion is first given of the requirements which must be met by systems of transpositions for telephone circuits in general, and by the new ``exposed line'' system in particular An outline is given of the methods used in the design work and the theory upon which it is based The diagrams in the paper show the arrangements of transpositions for all circuits on eight crossarms of telephone line The results to be obtained from the use of these diagrams are outlined, and the suitable locations of coordinate transpositions in parallel power circuits are discussed The application of these and other arrangements of coordinated transpositions to specific cases must take into account the variations in separation and other changes in the power and telephone circuits It is considered to be beyond the scope of the present paper to go into a discussion of the problems involved in these specific applications

Journal Article•DOI•
TL;DR: In this paper, a detailed description of the principle and construction of the thermal storage demand meter is presented, wherein it always indicates what may be called ''logarithmic average'' rather than ''arithmetic average'' of power consumption, heretofore indicated by practically all demand meters.
Abstract: Following a detailed description of the principle and construction of the thermal storage demand meter the author shows wherein it always indicates what may be called ``logarithmic average'' rather than ``arithmetic average'' of power consumption, heretofore indicated by practically all demand meters. The inherent faults of the ``arithmetic average'' or ``block interval'' meter are described and examples given demonstrating that the thermal storage meter alone recognizes the true heating effect that fixes size of equipment and therefore cost that should be assessed against the customer.


Journal Article•DOI•
TL;DR: In this paper, a short history of lightning protection of electric systems is given, as relating to the three successive types of electric circuits; the communication circuits, the power circuits of negligible electrostatic capacity, and the high-power circuits containing distributed capacity and inductance and capable of electric oscillation.
Abstract: A short history of lightning protection of electric systems is given, as relating to the three successive types of electric circuits; the communication circuits, the power circuits of negligible electrostatic capacity, and the high-power circuits containing distributed capacity and inductance and capable of electric oscillation, leading to the three problems of discharging over-voltage to ground, opening the power current which follows the discharge and discharging so that no power current follows even for a fraction of a half wave. It is shown that these problems are solved by the spark gap to ground, by the use of non-arcing metals in the multigap arrester, which opens the circuit at the end of a half wave of current, and by the so-called ``counter e.m.f.'' type of arrester, represented by the aluminum cell and the oxide film arrester. It is shown that the necessity of taking care of recurrent discharges in high-power systems had led to the universal adoption of the aluminum cell arrester in such systems, in spite of its disadvantage of requiring daily attendance in charging, and of containing an electrolyte and oil. In the oxide film arrester a type of arrester is presented which has the same characteristics and therefore the same advantages as the aluminum cell arrester, but does not require daily attendance and contains no liquids.

Journal Article•DOI•
TL;DR: In this article, the principal steps in the experimental development of high-speed circuit breakers and flash barriers are briefly given, and the importance of arranging the connections to the brush rigging so that the magnetic action on the arc will be a minimum, and properly directed, so the flash will do the least damage.
Abstract: The equipment developed for the protection of direct-current apparatus as described in this paper is applicable to all direct-current apparatus and all methods of operation. Special means of protection for use only with particular apparatus or conditions of operation have not been mentioned. The principal steps in the experimental development of high-speed circuit breakers and flash barriers are briefly given. The protection afforded by the high-speed breaker or barriers is sufficient for most apparatus and service, but complete protection for any direct-current apparatus and service requires both the high-speed breaker and flash barriers. Attention is directed to the importance of arranging the connections to the brush rigging so that the magnetic action on the arc will be a minimum, and properly directed, so the flash will do the least damage.

Journal Article•DOI•
TL;DR: In this article, it was shown that the flux distribution in the air gap of a synchronous machine consists of a series of component distributions that are simple harmonic wave trains, either stationary or moving at constant velocities.
Abstract: It is shown that the flux distribution in the air gap of a synchronous machine consists of a series of component distributions that are simple harmonic wave trains, either stationary or moving at constant velocities. Methods are suggested for determining the effects of slots and the saturation of the magnetic circuit on the magnitudes of these component distributions. Expressions for the voltage generated and the power developed thereby are given. The theory is applied to the operation of a three-phase synchronous machine under different conditions of load, both qualitatively and quantitatively. A table of comparative calculated field currents is appended.

Journal Article•DOI•
TL;DR: In this paper, the main causes of pin-type insulator failures in service are discussed, and the necessary modifications of the theoretical designs, in order to meet operating and manufacturing conditions, are discussed.
Abstract: The paper first gives a summation of the items that are apparently the main causes of pin-type insulator failures in service. Each item is thereafter briefly discussed and the opinions of operating men are cited. A brief description is given of the method used to determine the form of the dielectric field about porcelain insulators under normal line voltage. Diagrams of the dielectric fleld and photographs of flash over tests of theoretical designs are shown. There-after, the necessary modifications of the theoretical designs, in order to meet operating and manufacturing conditions, are discussed. In the latter part of the paper, diagrams and illustrations are shown of a proposed type of commercial insulator design which has been evolved by linking together the theoretical and practical phases of the problem. A comparison is then made between the older types of design and the proposed type, as regards the resistance of each to the conditions that cause failure of the insulator in service. In conclusion, a summary is made of the advantages it is believed that the new type of design has over the present commercial insulator designs.

Journal Article•DOI•
TL;DR: In this paper, a method of studying the single-phase induction motor is presented, based on the assumption of two equal and oppositely rotating primary magnetomotive forces combined with a synchronously rotating secondary m.m. f.
Abstract: This paper covers a method of studying the actions of the single-phase induction motor, which the writer has found to be very convenient from the educational standpoint. It is based upon the assumption of two equal and oppositely rotating primary magnetomotive forces combined with a synchronously rotating secondary m. m. f., such as would be produced by direct-current excitation. It follows that there is a resultant rotating primary field just as in the polyphase motor, while in the secondary there are two currents, one of low frequency, corresponding to the polyphase motor, and the other of nearly double the primary frequency. Diagrams and descriptions are given to illustrate the magnetomotive forces and fluxes, showing how, among other conditions, two oppositely rotating fields of unequal value may be possible. The next step is a consideration of e. m. f. generation by two oppositely rotating fields, showing how both must be taken into account. The effects upon the counter e. m. f. and excitation, of the reduction or suppression of one field is shown. This illustrates, in a simple manner, why the excitation on single-phase must be practically the same as on polyphase at full speed and falls to one-half value at standstill. The full-load conditions are next considered. A comparison is made between a two-motor unit, consisting of two similar polyphase motors coupled together and connected for opposite rotation, and the straight single-phase induction motor. Various discrepancies are pointed out between the resultant action of the two-motor unit and the single-phase.

Journal Article•DOI•
TL;DR: In this article, the Committee on Industrial and Domestic Power (COPPP) has compiled a list of machinery used in the cement industry and the sizes and types of motor best adapted for the work.
Abstract: This paper has been compiled by the Committee on Industrial and Domestic Power to give general information regarding the different classes of machinery used in the cement industry and the sizes and types of motor best adapted for the work. The paper gives, first, a brief description of the process. This is followed by an outline of the various kinds of machinery used together with data as to power requirements. The types of motor best suited to each application together with starting characteristics, overload capacity, torque and other features are indicated.

Journal Article•DOI•
TL;DR: A brief discussion of inductive interference in general is first given, including reference to the work of the Joint Committee on Inductive Interference in California as mentioned in this paper, and various possible means for reducing such interference considered.
Abstract: A brief discussion of inductive interference in general is first given, including reference to the work of the Joint Committee on Inductive Interference in California. Inductive interference due to electrified railroads is then taken up and various possible means for reducing such interference considered. A description is given of four important installations of railroad electrification and the specific means adopted in each case for preventing interference, with the degree of success which has been met with.

Journal Article•DOI•
TL;DR: In this paper, the authors describe some corona tests which were made in Peru on a 70-mile transmission line located at an average altitude of 13,300 feet and the voltages range from 40,000 to about 72,000.
Abstract: This paper describes some corona tests which were made in Peru on a 70-mile transmission line located at an average altitude of 13,300 feet. The voltages range from 40,000 to about 72,000. The method employed in the tests is described and the calculations are given. The corona losses were found by subtracting the core and copper losses of the transformers and the line copper losses due to the line charging currents from the total loss measured. Core-loss tests were made on the transformers in order to check these against the shop tests. The highest voltage experimented with was 72,300 when a corona loss of 153 kw. was found, or a little over two kw. per mile of line. The results are compared to ``Peek's law'' and a wide divergence found, amounting to over 800 per cent at about 66,000 volts and a loss of 58 kw. Close correspondence is found between these tests and those made by Faccioli on the Shoshone-Leadville line, and the equation of the loss-voltage curve obtained is the same as was established by Faccioli, and shows this relation to be logarithmic and not quadratic for the voltage range investigated. It is shown that the results are in good agreement with the formulas deduced by Professor Ryan from extensive laboratory tests. Finally test data are given for a test made during rainy weather and this shows no appreciable difference from tests made during fair weather.

Journal Article•DOI•
TL;DR: In this article, it was shown that the B-curve under load will not differ radically from the no-load field form since the fundamental will remain large enough to hold its own.
Abstract: It is shown in Section IV that with the ordinary field forms met with in practise, the resultant flux wave under s. s. c. (sustained short circuits) will be extremely distorted, see Figs. 16, (4th wave) 23, 27, 27A, etc., for the simple reason that with the very low voltages obtained under such conditions, the fundamental of the B-curve of the field is reduced so much by the armature reaction that the higher harmonics assume a very predominant role and become several hundred per cent of the s.s.c. fundamental. See Fig 26 and Tables XI, XII, and XIII. As a corollary to the foregoing it is found that the B-curve under load will not differ radically from the no-load field form since the fundamental will remain large enough to hold its own. See Fig. 22 and also footnote (4). The cross magnetizing effect of the armature reaction is, of course, to make the B-curve unsymmetrical with respect to the mid-pole axis. Compare Figs. 7 and 22. The magnetic oscillations are studied not only by means of full-pitch stator coils but also by means of rotor coils No. 7 and 8, Fig. 3, and stator coils No. 9, 10, 11, 12, 15, and 16, Figs. 3 and 3A. Attention is called to the following facts for which explanations and theoretical proofs are offered. (1) The ripples at the crest of the e. m. f.

Journal Article•DOI•
TL;DR: In this paper, a new form of high-voltage lightning arrester gap called the impulse protective gap is described, which has been called the ''impulse protective gap'' because of its particular effectiveness in protecting against line disturbances of steep wave front.
Abstract: This paper describes a new form of high-voltage lightning arrester gap which has been called the ``impulse protective gap'' because of its particular effectiveness in protecting against line disturbances of steep wave front. The paper opens with a brief resume of some of the results of previous investigations of the subject of impulse voltages. A discussion of the points involved in securing adequate protection against transient voltages of steep wave front follows. Particular reference is made to some of the conditions that may exist when a high-frequency impulse is superimposed on a low-frequency wave. In this connection is shown the desirability of a gap having a selective action, making it sensitive to steep wave fronts, and a number of forms of gap having this selective property are described. Methods employed in testing these gaps are described and the results of a large number of experiments are tabulated. Tests on the action of a high-frequency impulse combined with a 60-cycle wave are included in the experimental work. From the experimental data a number of curves are plotted showing the discharge characteristics of the impulse protective gap under many different conditions. The results of the tests are highly favorable and indicate that the new gap may have a wide application in the field of lightning protection.




Journal Article•DOI•
TL;DR: In this paper, the authors considered the case of two or more pre-charged condensers in series, and derived equations similar to Kirchoff's laws to determine the final distribution of voltages among them.
Abstract: A condenser is charged from a source of direct voltage, and then is used as a booster in series with this source to charge another condenser. By repeating this process a large number of times the second condenser is finally subjected to twice the voltage of the source. This is the principle of the Delon apparatus for testing cables, and is explained in a numerical example. Then the more general case of two or more ``pre-charged'' condensers in series is considered, when these condensers are connected to some source of direct voltage; it is shown how to determine the final distribution of voltages among them. A similar problem is solved for pre-charged condensers in parallel. Finally a general network of pre-charged condensers is considered, and equations are derived similar to Kirchoff's laws, from which the final distribution of voltages and charges may be computed knowing the initial distribution.