Showing papers in "Transactions of The American Institute of Electrical Engineers in 1911"

The Law of Corona and the Dielectric Strength of Air-II

Abstract: For several years an extensive investigation on the dielectric strength of air, and more particularly, on the law of corona, has been carried on by the Consulting Department of the General Electric Company, under the general supervision of Dr. C. P. Steinmetz. The facilities were practically unlimited in regard to power, apparatus, instruments and their standardization, and available engineering skill. Thanks for their active assistance in this investigation are due to Dr. E. J. Berg, Messrs. C. M. Davis, J. L. R. Hayden, A. B. Hendricks, W. K. Page, L. T. Robinson, L. A. Schloss, W. I. Schlicter, C. W. Stone and J. B. Taylor.

The Electric Strength of Air.-II

Abstract: In a former paper 1 with the title of the present one the author described a series of investigations of the conditions under which the air breaks down in the neighborhood of clean, round wires subjected to high voltage. A principal feature of that paper was the description of a method for observing with a close degree of accuracy the critical or corona voltage for various sizes of wire when centred in cylinders forming the opposite side of the source of voltage. There has been a great diversity in the values of critical voltage as given by other observers, who for the most part have used the appearance of the visible corona and the readings of instruments in the primary circuits of transformers as indications of the voltage at which the air breaks down. The method referred to was developed as the result of a conviction that the laws governing the loss between high-tension lines could not be satisfactorily determined without a study and knowledge of the fundamental phenomena. So far therefore these investigations have been concerned only with the conditions under which the air actually breaks down causing a large increase in conductivity and power loss. The results of the former paper show among other things that when corrected for wave form, temperature and pressure the electric intensity at the surface of a clean, round conductor, corresponding to the voltage at which corona starts and loss sets in is a constant for each size of wire. This value of surface intensity varies with the temperature and pressure and is that corresponding to the maximum value of the voltage wave. It is different for different sizes of wire but is independent of the material of the wire, of the moisture content, and of the amount of free ionization in the air. In the present paper some further facts bearing on the fundamental relation between diameter and critical surface intensity are given, and a series of investigations of the influence of stranding a conductor, of variations of atmospheric pressure, and of frequency on the critical electric intensity are also described.

Cisoidal Oscillations

Abstract: The oscillations here defined as “cisoidal oscillations” are those of the form

The Commercial Loading of Telephone Circuits in the Bell System

Abstract: The year 1900 may be considered to have marked the beginning of a very important period in the development of telephony. For some time prior to that date it had been known to those who gave study to the matter that the transmission efficiency of long telephone circuits would be improved by increasing the uniformly distributed inductance of the circuit. This knowledge, however, did not lead to any direct commercial results for the reason that no one was able to point out any practical method of increasing the distributed inductance of a telephone circuit without bringing in difficulties of one kind or another which were fatal.

Design, Construction and Test of an Artificial Transmission Line

Abstract: A little over a year ago Dr. Steinmetz suggested the construction of an artificial transmission line or “slow-speed conductor” in the Electrical Laboratory at Union College. It was proposed to duplicate or reproduce as nearly as possible the conditions of a high-voltage long-distance transmission line in the laboratory in such a way that the various phenomena connected with a line of this sort might easily be investigated. It was not desired particularly to study the effects of very high voltage but rather to investigate and study the various transient and other phenomena in connection with switching, sudden change of load, etc.

A Power Diagram Indicator for High-Tension Circuits

Abstract: Introduction and Summary The power diagram indicator was produced as a feasible, inexpensive instrument to observe dielectric or similar stray power losses that occur in high-tension circuits. 1 A cathode ray-pointer is used to trace the power diagram. It is actuated electrostatically. The pressure of the high-tension circuit applied to “quadrants” causes a proportional displacement of the ray-pointer in one axis; the pressure drop between the terminals of a condenser in series with the high-tension circuit is applied to the other pair of quadrants and gives the ray-pointer a quadrature velocity proportional to the current. The ray-pointer is thus made to trace a diagram that encloses an area proportional to the e.m.f.-current-time product. 2 Alternating current will produce a closed diagram or “card” having an area which is proportional to the energy of the circuit delivered per cycle. At constant frequency, therefore, the card-area measures the power applied in the circuit. The form of the card tells of many things besides the amount of power just as the steam-engine indicator card does in steam engineering.

The High-Efficiency Suspension Insulator

Abstract: The high-efficiency type of suspension insulator has become an important factor in high-tension transmission within the last few years, and it is hoped that the considerations which led to the design of this type will be of interest.

Electrolytic Corrosion in Reinforced Concrete

Abstract: While reinforced concrete was coming into general use as a structural material much space in the technical press was given to discussions and reports on the durability of the encased iron. The results from a large number of experiments gave fairly conclusive evidence that under ordinary conditions the iron is protected, and that even if it was rusty when placed in the concrete, it will be free from the oxide after remaining in the concrete for some time. The time test on the durability of practical structures is, of course, the final arbiter, and for each year the increasing data bears out the assumption that properly constructed concrete-steel structures will stand indefinitely.

Electrically Driven Reversing Rolling Mills

Abstract: The load conditions under which motors driving continuous running rolling mills operate is generally understood, and the advantage to be obtained by using a suitably designed flywheel is well known. Owing to the rapidly fluctuating load, some system of energy storage capable of performing a large amount of work for short periods must obviously be of considerable value not only from the standpoint of motor operation but also from that of power supply. Several papers have been read before this Institute dealing with the question of the action of flywheels with such loads and the advantage has been clearly demonstrated. The value of flywheels can be best appreciated when used with mills with very high and short peak loads, such as a blooming mill, where loads up to 10,000 h.p. for one or two seconds are not infrequent. The antithesis of this type of mill is the reversing mill where every effort is made to reduce the flywheel effect to a minimum so that the accelerating force required may be kept within reasonable limits. Most engineers connected with industrial work are familiar with the development of electrically driven continuous running mills but the development of the reversing mill is not generally appreciated except by those more or less connected with their design and operation. The object of this paper is to briefly review some of the more important points in its design and operation.

The Effect of Temperature upon the Hysteresis Loss in Sheet Steel

Abstract: In the experiments described below, investigations were made upon the variation in hysteresis loss in sheet steel when passing from ordinary atmospheric temperatures up to the point at which the material becomes non-magnetic. The measurements were made over as wide a range of induction as possible. In order to get consistent results it was found to be important that the observations at each temperature be made quickly, partly on account of the difficulty of holding the temperature constant and partly because, even with constant temperature slow changes occurred in the hysteresis which become especially pronounced at the higher temperatures.