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Showing papers in "Transactions of The American Institute of Electrical Engineers in 1944"


Journal ArticleDOI
TL;DR: In this article, the authors discuss the mechanism by which inrush currents are produced, the results of tests and calculations, and studies made with the miniature-system analyzer, and factors that determine the significance, of inrush current from the standpoint of system operation.
Abstract: When a transformer is energized, a transient current, known as magnetizing inrush current, generally flows for a short period of time until normal flux conditions are established. Under most practical system conditions, this current transient is of little consequence. However, in very rare cases a combination of circumstances may be obtained which results in this inrush being of such consequence as to impair momentarily the proper operation of the system. Because of the numerous faetors bearing upon this general problem, an investigation has been made to determine the effects of transformer inrush currents under a wide variety of system conditions. It is the purpose of this paper to discuss the mechanism by which inrush currents are produced, the results of tests and calculations, and studies made with the miniature-system analyzer. Factors that determine the significance, of inrush current from the standpoint of system operation and methods for reducing the inrush current or mitigating its effects are also discussed.

85 citations


Journal ArticleDOI
TL;DR: The fact that voltage regulators may on occasion increase the stability limit is more or less well known as mentioned in this paper, and the present paper aims to contribute to the knowledge of the subject by:
Abstract: STEADY-STATE stability of synchronous machines is an old subject, and the fact that voltage regulators may on occasion increase the stability limit is more or less well known.1 The present paper, however, aims to contribute to the knowledge of the subject by:

77 citations


Journal ArticleDOI
TL;DR: The magnitude and wave shape of discharge currents in 46 direct strokes have been measured during a five-year period at 25 direct stroke stations on structures ranging in height from 75 to 585 feet.
Abstract: The magnitude and wave shape of the discharge currents in 46 direct strokes have been measured during a five-year period at 25 direct-stroke stations on structures ranging in height from 75 to 585 feet. Measurements have been made with instruments capable of recording the wave front and tail of the high-current peaks and the low-magnitude continuing currents to as low as 0.1 ampere. These data are correlated with 138 special camera photographs of strokes to open ground obtained in this investigation, with similar photographs taken in South Africa and with stroke current measurements made on the Empire State Building in New York City. Most strokes to structures, less than 600 feet high, appear to have discharge characteristics essentially the same as those to open ground. Their probability of being struck is about proportional to height, being in the order of two strokes per year for 500-foot structures and 0.3 per year for 100-foot structures. Whereas practically all strokes to the 1,250-foot Empire State Building are initiated by an upward streamer propagating from the building to the cloud, only four such strokes have been recorded in this investigation: three out of 13 strokes to a 585-foot stucture and one out of 13 to a 360-foot structure. Strokes of this type, as recorded here and to the Empire State Building, had discharge currents consisting principally of a continuous flow of low-magnitude current upon which the high-magnitude short-duration peaks are superimposed.

65 citations


Journal ArticleDOI
TL;DR: The necessity of considering for many practical problems the electrical and mechanical transient phenomena simultaneously in induction-motor transient problems simultaneously is shown.
Abstract: IT has been the usual practice to solve induction-motor transient problems either on the basis of the familiar steadystate equivalent circuit or by calculations which require simplifying assumptions. These methods neglect important factors determining the performance. This paper shows the necessity of considering for many practical problems the electrical and mechanical transient phenomena simultaneously.

61 citations


Journal ArticleDOI
TL;DR: The system load of an electric power company may be regarded as having several components as mentioned in this paper : a fixed component of the system load that may be considered as reflecting the business activity of the territory of the company, and a variable component of load that reflects the effect of the weather.
Abstract: THE system load of an electric power company may be regarded as having several components. Firstly, there is a fixed component of the system load that may be considered as reflecting the business activity of the territory of the company. Secondly, there is a variable component of the load that reflects the effect of the weather. Thirdly, there is a component of load, relatively infrequent in occurrence, that reflects the public response to events of unusual attraction. There is the positive effect on the load of the appeal of radio broadcasts of great local or national interest and the negative effect that evidences the influx of the buying public into shopping areas which reaches its peak in the Christmas period.

28 citations


Journal ArticleDOI
TL;DR: In this paper, a wide range of power output, voltage, current, and speed of the d-c and a-c machines were evaluated for best commutation, while others were partially compensated, and still others were without compensation and depend on the brush shift and brush grade for satisfactory operation.
Abstract: THE rapid development of military aircraft during the past three years has been accompanied by an equally vigorous development and use of electric motors and generators necessary for their operation and control. This dynamoelectric equipment covers not only the d-c and a-c applications but also a wide range of power output, voltage, current, and speed. Some of the d-c machines are compensated fully for best commutation, while others are partially compensated, and still others are without compensation and depend on the brush shift and brush grade for satisfactory operation.

24 citations


Journal ArticleDOI
TL;DR: In this paper, the authors calculate the parasitic torques and forces produced by the harmonics in induction motors and salient-pole synchronous machines based on exact knowledge of the leakage with respect to the harmonic components.
Abstract: THE calculation of parasitic torques and forces produced by the harmonics in induction motors and salient-pole synchronous machines is based on exact knowledge of the leakage with respect to the harmonics and especially on the knowledge of the differential leakage.

24 citations


Journal ArticleDOI
TL;DR: In this article, the authors present a complete analysis giving the essential formulas in a systematic and unified form readily usable by the engineer, and present a treatment of the general principles employed in the analysis of rectifier circuits.
Abstract: THE general principles employed in the analysis of rectifier circuits have been quite fully covered in the literature and are now well understood. However, there is not available a complete analysis giving the essential formulas in a systematic and unified form readily usable by the engineer. It is the purpose of this paper to present such a treatment.

24 citations


Journal ArticleDOI
TL;DR: Brownlee et al. as discussed by the authors presented a quantitative analysis of the many design and application factors governing transformer magnetizing inrush currents, which is useful from the standpoints of system planning and operation, not only in connection with units employing the newer high-permeability iron but for the solution of existing problems involving transformers with conventional iron.
Abstract: W. R. Brownlee (Commonwealth and Southern Corporation, Jackson, Mich.): The quantitative analysis presented of the many design and application factors governing transformer magnetizing inrush currents should be most useful from the standpoints of system planning and operation, not only in connection with units employing the newer high-permeability iron but for the solution of existing problems involving transformers with conventional iron.

23 citations


Journal ArticleDOI
J. H. Hagenguth1
TL;DR: In this article, the importance of failure detection and means available at present are discussed at length and a new method is proposed which is more sensitive than the older methods and appears to be less subject to individual interpretation.
Abstract: Impulse testing of transformers has resulted in improvement of design and manufacturing methods Not only should the test methods now given in American Standard C572 be simplified to effect a reduction in cost of tests, but the test code should be modified to give an adequate assurance of failure detection The importance of failure detection and means available at present are discussed at length A new method is proposed which is more sensitive than the older methods and appears to be less subject to individual interpretation

23 citations


Journal ArticleDOI
TL;DR: In this article, a reentrant cylindrical cavity was adapted to measure the dielectric constant and power factor of small disk samples of insulating materials, and the methods of measurement, mechanical details, and electric coupling and detecting circuits all were described.
Abstract: A re-entrant cylindrical cavity has been adapted to measure the dielectric constant and power factor of small disk samples of insulating materials. The methods of measurement, mechanical details, and electric coupling and detecting circuits all are described. A single cavity can be utilized only over a frequency range of about 1.5 ratio from lowest to highest frequency. Therefore, several different-sized cavities would be required to cover a range of frequency from 50 to 1,000 megacycles. An accuracy of ±0.00005 in tan ? and ± 1 per cent in dielectric constant may be obtained in routine measurements. Because the cavity has a very high Q(≫2,000), it is much more sensitive to low-power-factor dielectric samples than any conventional coil-and-capacitor resonant circuit. The chief advantages of this method are that the operation of the apparatus is simple, very rapid, and similar to the susceptance variation technique now used at lower radio frequencies. Also, the involved computations usually found in other methods operative in this frequency range are eliminated.

Journal ArticleDOI
TL;DR: In this article, the authors present some of the considerations involved in selecting electric systems for large aircraft and present a brief review of the basic factors involved in the design of such systems.
Abstract: This paper presents some of the considerations involved in selecting electric systems for large aircraft. Such systems are undergoing intensive development now; consequently it is not possible to give complete answers to all problems which arise. Also, certain parts of the electric systems are subject to military classification and cannot be discussed. Nevertheless it is felt that many engineers, particularly those engaged in the design of such systems, will welcome a brief review of the basic factors involved. Industrial and central-station experience provide a valuable background for study of aircraft systems. However, too close an adherence to previous practice should not be maintained, since aircraft systems differ in many ways from those of land equipment. The need for minimum weight demands that only those features be included which fundamental considerations show to be necessary or which at least provide benefits that justify the weight involved.

Journal ArticleDOI
TL;DR: In this paper, the results of an extended series of thermal tests on a variety of dry-type transformer coils are given in regard to the effect of different heights of coil stacks, different configurations, and essential precautions in making temperature measurements are pointed out.
Abstract: With the increasing use of dry-type transformers, attention has been focused upon the fact that the difference between the average temperature rise by resistance and the hottest-spot temperature rise is much greater than in liquid-immersed transformers. In this paper there are given the results of an extended series of thermal tests on a variety of dry-type transformer coils. Data are presented in regard to the effect of different heights of coil stacks, different configurations, and, in addition, some essential precautions in making temperature measurements are pointed out. Hot-spot temperatures were investigated in coils cooled by natural draft and by forced-air circulation at different velocities for both directed flow and random flow. Sufficient data are given to determine the ratio between the average temperature rise of the windings and the hottest-spot temperature rise. Based upon this relationship, the need is shown for review and modification of the conventional hot-spot allowances for dry-type transformers.


Journal ArticleDOI
TL;DR: In this article, a 14-integrator differential analyzer was used by the General Electric Company at Schenectady, New York, for the measurement of torque amplifiers.
Abstract: This paper describes a new 14-integrator differential analyzer recently placed in service by the General Electric Company at Schenectady. This analyzer has a mechanical interconnection system but has integrators of novel design in that a Polaroid follow-up system is used rather than the more usual mechanical torque amplifiers.

Journal ArticleDOI
TL;DR: A field survey and laboratory tests are presented in this article showing the relationship between loading, conductor-temperature changes, movement in manholes and ducts, and sheath life for paper and lead cable.
Abstract: Results of a field survey and laboratory tests are presented in this paper showing the relationships between loading, conductor-temperature changes, movement in manholes and ducts, and sheath life for paper and lead cable. The record on underground 15-kv cable is included to emphasize the noninherent failures attibutable to physical proportions of underground structures. Improvements in modern cable have permitted operation at increasing temperatures with few inherent failures. The tests and operating experience indicate that unsatisfactory sheath life caused by fatigue of lead can result from cyclic tempratures allowed in standard cable specifications. A method is outlined for computing sheath strains for given cable off-sets and movements at the duct mouth. Fairly reasonable estimates of sheath life can be prepared. The tests indicate also that snaking of cable within the ducts may impose severe cyclic strains on the lead and become the determining factor for optimum sheath life.

Journal ArticleDOI
TL;DR: In this article, it has been realized that the surest and most effective way to obtain simultaneous breaker operations at both ends of a transmission line, regardless of the location of a fault within the line section, is by use of some form of pilot channel relaying.
Abstract: IT has long been realized that the surest and most effective way to obtain simultaneous breaker operations at both ends of a transmission line, regardless of the location of a fault within the line section, is by use of some form of pilot channel relaying. Two forms of this type of protection have been developed and used very successfully for a number of years. One system is the familiar distance-type carrier relay system, and the other is the single-element differential pilot-wire system.

Journal ArticleDOI
TL;DR: In this article, the causes of electric machinery vibration are discussed, including the agencies which give rise to this particular type of vibration, and methods by which they may be controlled to keep the resultant vibration to a satisfactory minimum.
Abstract: Vibration in electric machinery is the result of a number of contributing agencies, some mechanical, others electromagnetic in origin. Features of mechanical and electrical design and construction which give rise to these agencies are discussed. The general character of the vibration which each agency produces is explained, as well as how different agencies combine to produce the resultant machine vibration. Where excessive vibration is encountered in the field, methods are outlined for ascertaining the major agencies responsible so that corrective modifications may be made which will be effective in reducing the resultant vibration. These methods are applied to motor-generator sets driven by two-pole induction motors to ascertain the cause of a particular type of vibration characterized by the vibration amplitude increasing and decreasing in uniform cycles twice during each revolution of motor slip. In this way the agencies which give rise to this particular type of vibration are explained, and methods by which they may be controlled to keep the resultant vibration to a satisfactory minimum are discussed.

Journal ArticleDOI
TL;DR: A number of load curves may be added to determine some characteristics of a composite load from known values of the individual loads which comprise it, such as peak load, minimum load, load factor, or time of the peak as discussed by the authors.
Abstract: A NUMBER of load curves may be added to determine some characteristics of a composite load from known values of the individual loads which comprise it. The resulting peak load, minimum load, load factor, or time of the peak are characteristics usually sought, but there may be many others.

Journal ArticleDOI
TL;DR: In this paper, a simple and straightforward basis for machine protection which affords the increased protection and saving in installation cost and material that it was found possible to achieve was presented. But, in view of the statistical data that have been accumulated in extensive lightning investigations, and the appreciation of the value of the inherently low discharge voltage characteristics of the deion arrester, it has been considered desirable to study this problem further.
Abstract: The high monetary value and low insulation levels of rotating machines make it necessary to employ special protection. A rotating machine can be conceived as a transmission line with distributed constants, the essential difference being that the machine winding is wound back on itself in the form of turns, which may permit high voltage across the turn-to-turn insulation. The installation of special arresters with low and consistent spark-over characteristics will limit satisfactorily the maximum voltage that can appear across the terminals. However, capacitors also are required which, in conjunction with the inductance in the line, slope the front of the wave and thus prevent pilin up of voltage across the turns. Present methodsl1-7 of protection, on the whole, have proved quite satisfactory. However, in view of the statistical data that have been accumulated in extensive lightning investigations,8-12 the recognition of the importance of providing good grounding for the line arresters, and the appreciation of the value of the inherently low discharge voltage characteristics of the deion arrester, it has been considered desirable to study this problem further. The more important results of this study are summarized here with the viewpoint of providing a simple and straightforward basis for machine protection which affords the increased protection and saving in installation cost and material that it was found possible to achieve. Although the protection required at the machine and in the line are mutually interdependent, it is possible to resolve the suggestions for protection into the four following categories: A.

Journal ArticleDOI
N. R. Stansel1
TL;DR: Induction heating is an application of the theory of the eddy-current phenomenon as mentioned in this paper, which is a general definition of induction heating is the use of eddy currents to raise the temperature of a conducting mass.
Abstract: THE general definition of induction heating is the use of eddy currents to raise the temperature of a conducting mass. Thus induction heating is an application of the theory of the eddy-current phenomenon.

Journal ArticleDOI
TL;DR: Power-line carrier has kept pace with the swift progress of the electronic art during the last several years as discussed by the authors and has been expanded to include as many functions as possible consistent with reliability, economy, and convenience.
Abstract: Power-line carrier has kept pace with the swift progress of the electronic art during the last several years. This progress has been due mainly to the stimulus injected by the war effort. In most of the specialized fields of electronics, the advancement was necessitated and promoted strictly for military purposes. Power-line carrier, however, was and is the soldier of the home front. Its duties have been expanded to include as many functions as possible consistent with reliability, economy, and convenience. The economic feature is especially significant now, since, during wartime emergencies, the material resources of the nation are allotted, and properly so, to those agencies concerned with the battle front. Material for new power lines, new generating equipment, new telephone lines, and for other similar programs of expansion is therefore not generally available. However, power-line carrier comes to the rescue and effectively provides additional circuits and higher power-handling capacity for existing installations.

Journal ArticleDOI
TL;DR: The recording of lightning currents with surge-crest-ammeter links began in 1934 and 5,501 bracket records have been obtained from transmission towers aggregating 13,227 tower-years of exposure as discussed by the authors.
Abstract: 1. The recording of lightning currents with surge-crest-ammeter links began in 1934. In the ensuing years through 1942, 5,501 bracket records have been obtained from transmission towers aggregating 13,227 tower-years of exposure. There have been 54 sets of records from lightning arresters, obtained during 155 bank-years of experience. 2. Based on an eight-year period of record in one case and a five-year period in the other, two similar 220-kv lines running in a generally north-south direction experienced the same average number of strokes per year within approximately seven per cent. Two similar 66-kv lines lying in an east-west direction experienced the same average number of strokes, within about three per cent, during a seven-year period. 3. A 132-kv line, having about the same span lengths as a 220-Kv line but lying in a more or less northwest-southeast direction within about two miles of a river throughout its length, experienced on the average about 40 per cent more strokes per unit length than the 220-kv line during an eight-year period. 4. The maximum number of strokes recorded on one of the transmission lines in one year was 4.9 times the minimum number recorded in another year. The maximum number on this line occurred in the same year that the minimum number occurred on a comparable line. 5. The strokes in single years to a line deviated up to 89 per cent from the seven- or eight-year averages.

Journal ArticleDOI
TL;DR: In this article, the authors provide a history and evolution of the electronic converter, its use in the suppression of electronic faults and in the single-conversion frequency changer, and a description of the dc transformer.
Abstract: The authors feel the term "electronic power converter" needs some definition. The object may be to convert power from direct current to alternating current for direct current (dc) power transmission, or to convert power from one frequency into another,or to serve as a commutator for operating an ac motor at variable speed,or for transforming high-voltage dc into low-voltage dc. It is thus evidently not the objective but the means that characterizes the electronic power converter. The emphasis is on electronic means and the term is limited to conversion of power as distinguished from electric energy for purposes of communication. Thus, the name is a definition. The authors provide a istory and evolution of the electronic converter, its use in the suppression of electronic faults and in the single-conversion frequency changer. Finally a description is given of the dc transformer and the adaptability of the electronic converter.

Journal ArticleDOI
TL;DR: In this article, a co-ordinated study has been made on the impulse strength of insulated power cables having various types of insulation and their accessories, and tabulations of safe withstand impulse voltages have been prepared.
Abstract: Pursuant to a request of the cable working group, AIEE committee on power transmission and distribution, a co-ordinated study has been made on the impulse strength of insulated power cables having various types of insulation and their accessories. The data included not only all published information, but also much privately contributed information. On the basis of these data and some supplementary tests recently made, tabulations of safe withstand impulse voltages have been prepared. The information is also discussed with regard to its significance for practical applications from the standpoint of switching surges as well as from the standpoint of lightning impulses. Recommendations are given for standardizing impulse-test procedures.

Journal ArticleDOI
TL;DR: The first 20,000-kw electronic power converter was made in December 1943 at the Edgar Thompson plant of the Carnegie-Illinois Steel Corporation to exchange power between their 25-cycle 44kv and 60-cycle 69kv systems, the latter being connected to a large public utility.
Abstract: The installation of the first 20,000-kw electronic power converter was made in December 1943 at the Edgar Thompson plant of the Carnegie-Illinois Steel Corporation to exchange power between their 25-cycle 44-kv and 60-cycle 69-kv systems, the latter being connected to a large public utility. The converter operates in parallel on both systems with normal generators. This type of converter was selected to obtain its ease and simplicity of control, low contributions to faults, light weight of indoor equipment, high efficiency, and ability to transfer a fixed value of power regardless of departure from normal frequency ratio between the two systems. The converter may have its power output controlled manually or by a power regulator or may reduce the demands for power taken from the 60-cycle utility system. Controls also may be supplied to a typical electronic converter to cause it to share the total load of the receiving system in a predetermined proportion with prime movers. Inherently transferring power in a preselected direction in relation to the departure from normal voltage ratios of the two systems, automatic phase control of grid excitation rapidly compensates for changes in this ratio. The reactive kilovolt-amperes needed for commutation, harmonics, and transformer magnetizing current of both rectifier and inverter is supplied by the synchronous machinery in the steel company's systems. Faults such as arc-backs and ``shoot-throughs'' in the electronic equipment are suppressed in a very short time period. The rectifier cannot furnish current to a fault in its supply system.

Journal ArticleDOI
TL;DR: In this article, a single-phase induction motor is given starting torque by varying the rotor constants over the pole face, either by asymmetrical iron structure or winding, and the starting torque is comparable with that of a shaded-pole motor.
Abstract: THE shaded-pole motor is quite simple to construct; but for all but the smallest sizes, losses are large; and if distributed windings are used, its construction becomes more complicated. A single-phase induction motor may be given starting torque by varying the rotor constants over the pole face, either by asymmetrical iron structure or winding. Starting torque is comparable with that of a shaded-pole motor, and construction is very simple with nothing to get out of order. The chief drawback appears to be the smaller power factor which is due to reduced mutual inductance.

Journal ArticleDOI
TL;DR: The pentode ignitron is a high-voltage tube used for rectification and inversion in electronic converters as discussed by the authors, which is a sealed steel tube having an anode, three grids, and a mercury-pool cathode.
Abstract: The name ``pentode ignitron'' has been applied to a high-voltage tube used for rectification and inversion in electronic converters. It is a sealed steel tube having an anode, three grids, and a mercury-pool cathode. The tube is of the gas-filled type with control characteristics similar to those of the thyratron. An ignitor establishes a cathode spot each cycle on the mercury pool. The cathode spot is stabilized at low anode currents by the use of an auxiliary holding anode. The functions of the three grids are somewhat similar to those in the pentode vacuum tube, but the manner of use is quite different. The first grid, or one nearest the anode, is used as an intermediate anode to divide potential gradients across the tube during nonconducting periods. The second, or center grid, is used to control the starting of the conduction period and the third, or outer grid, as a shield to permit rapid deionization of the space between the control and shield grids. The introduction of multiple grids in ignitron tubes provides certain characteristics which are essential to inverter operation. It is the purpose of this paper to describe some of these characteristics, and the design and construction of the pentode ignitron tube. These tubes are the ones installed in the power converter described in the companion papers.1,6-8

Journal ArticleDOI
TL;DR: Induction heating as mentioned in this paper is a technique that can be used to heat a piece of metal or other conducting material by wrapping a coil around the piece and causing a current of suitable magnitude and frequency to flow into the coil.
Abstract: HEAT can be generated in a piece of metal or other conducting material by wrapping a coil around the piece, such as the cylinder shown in Figure 1, and causing a current of suitable magnitude and frequency to flow into the coil. This is called “induction heating.” The great advantage of this type of heating is that the heating can be accomplished without contacting the piece to be heated. This allows the heating to take place while the piece is moving or enclosed in a protective atmosphere. Also, the heat usually can be concentrated just where it is needed, and a piece usually can be heated faster by induction than by any other method. The desirable frequency to use for induction heating depends on the size and the electrical properties of the piece to be heated and may vary from 25 or 60 cycles per second for heating joints in iron pipes to a few million cycles per second for heating very small nonmagnetic pieces for soldering. Frequencies up to 10,000 cycles per second are obtained usually from rotating machines; for higher frequencies one must resort to spark or vacuum-tube oscillators.

Journal ArticleDOI
TL;DR: In this article, the authors examined various definitions of inductance based on the application in which the term was used and made comparisons between the definitions as a function of magnetomotive force and flux density for the special case of dynamo-grade (2.75 per cent) silicon steel.
Abstract: It is the purpose of this paper to examine various definitions of inductance based on the application in which the term is used. Comparisons are made between the definitions as a function of magnetomotive force and flux density for the special case of dynamo-grade (2.75 per cent) silicon steel. The effects of hysteresis and eddy currents are discussed. Consideration is confined to iron magnetic circuits in which no air gap exists, so that practical applications of conclusions drawn are limited somewhat.