By Topic

American Institute of Electrical Engineers, Transactions of the

Issue 4 • Date April 1941

Filter Results

Displaying Results 1 - 11 of 11
  • The Service Factor Rating of Arc-Welding Generators and Transformers

    Page(s): 137 - 141
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1192 KB)  

    The primary purpose of rating an electrical machine is to give the user an idea of what he may expect from the unit which he purchases. It is the purpose of this paper to propose a method of rating arc-welding generators and transformers which will give a truer picture of their working ability than is afforded by the present one-hour rating. Such a method of rating will be beneficial both to the customer who buys and uses arc welders and to the manufacturers who produce and market the units. The user will be better able to select a machine which will do the job to be performed, and at the same time he will be assured that he is not purchasing a machine unduly large for his requirements. The present custom is to give welding transformers and generators a one-hour rating, specifying the current they can deliver for a one-hour period, starting cold, without exceeding the permissible temperature rise. The plan here proposed is to give them a current rating indicative of their normal operating capacity, or short-time welding ability; and an additional service factor rating, indicative of their continuous current capacity, as limited by thermal considerations. All electric apparatus has these two major limitations on its output, one a ``size'' limit expressed by breakdown torque, commutation limit, or voltage drop; and the other a thermal limit expressed by the degrees temperature rise permissible for the type of insulation used. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Engineering Requirements for Program Transmission Circuits

    Page(s): 142 - 147
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (3222 KB)  

    Present-day program networks are reviewed from the standpoints of engineering, design, and operation as developed to meet the needs of the broadcasters. The factors requiring consideration in the further development of program networks in anticipation of future needs are also discussed. The presentation of the paper is supplemented by a demonstration of the quality obtainable by transmission over various types of telephone facilities. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Prime-Mover Speed Governors for Interconnected Systems

    Page(s): 147 - 151
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1297 KB)  

    System operating requirements, from the standpoint of frequency and tieline loading, are continually becoming more rigorous and receiving more widespread attention. Supplementary controls have been developed to assist in the solution of these problems¿but the speed governors of the prime movers still constitute the backbone of system control. This paper outlines the general problems encountered; gives definitions of terms for both steam and hydro governors and discusses the performance characteristics of these two general classes of prime movers. As a result of discussions with several operating groups certain definite conclusions were reached for prime-mover governor characteristics on the larger systems, viz., dead band should be as small as practicable; uniform incremental regulation desirable; adjustable regulation not necessary; similar rates of response not necessary and accurate response to supplementary control desirable. These conclusions are supported by the analytical work presented in the companion paper.7 A summary of the reasoning supporting these conclusions under the subjects of stability, dead band, regulation, response, short circuits, and tie-line swings is included. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Analysis of Short-Circuit Oscillograms

    Page(s): 151 - 153
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (651 KB)  

    METHODS of analyzing the oscillograms of short circuit currents of synchronous machines, in accordance with the two reaction theory, are presented in this paper. Differences between the results found here and the more generally accepted equations, based on symmetrical components, are pointed out. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Full text access may be available. Click article title to sign in or learn about subscription options.
  • Full text access may be available. Click article title to sign in or learn about subscription options.
  • Displacement and Diffusion in Fluid-Flow Arc Extinction

    Page(s): 162 - 167
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (3390 KB)  

    The displacement and diffusion theories of arc extinction in flowing fluids are defined and contrasted. The question as to the possibility according to hydrodynamical principles of the formation of the wedge required by the displacement theory is considered and decided in the negative. Photographic evidence is also found to contradict the displacement theory. How turbulence will multiply diffusive effects is considered, and an estimate of l00fold multiplication is given for conditions existing in gas blast breakers. This enhancement of diffusion by turbulence is found to make the diffusion theory adequate for accounting for the circuit interrupting capacities of arcs in gas blast circuit breakers. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • System Stability

    Page(s): 168 - 173
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1509 KB)  

    That the specter of a major system shutdown is prominent in the thoughts of many operators is evidenced by the 1939 symposium, covering methods of modernization of station-switching facilities, and the 1940 symposium, discussing means of restoring service to systems after a major shutdown. In this paper, system and apparatus performances are studied, during the period between the time allotted for the functioning of the high-speed relay protection, and the point where the system becomes so unstable that a major shutdown occurs. With a view to the further improvement of system operation, the paper studies: 1. Phenomena preceding and during instability; 2. Method of lengthening the period between the fault and instability; 3. A local high-speed back-up relay scheme; 4. Means of automatically and quickly stabilizing an unstable system; and 5. In case all of the above fail, progressive isolation of the system by zones selected by degree of low voltage. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • The Water-Cooled Steel-Tank Rectifier Corrosion Problem

    Page(s): 173 - 178
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (4649 KB)  

    The first mercury-are rectifiers utilized glass tubes and consequently the physical size and electrical capacity was limited. The efforts to increase the available output led to the development of water-cooled steel-tank vacuum chambers after many years of research and the solution of many problems. This paper is primarily concerned with the solution of the problem presented by corrosion. Corrosion is essentially the returning of a metal to its original state and the problem consists in finding a means to retard the return sufficiently so that corrosion will not be a limiting factor in the life of rectifiers. Analysis of the problem indicates that pitting corrosion causes the greater damage and is largely a function of the character and condition of the metal, the quantity of electricity passing, and also that it is self- propagative. The rate of corrosion is affected by the temperature of the cooling water, the chemical constituency of the water, and potential differences between points on the surface of the rectifier tank. The first efforts in the solution of the corrosion problems were directed toward finding a protective coating to isolate the steel tank from the cooling water. Various paints, varnishes and lacquers, and enamels were investigated, as well as sprayed metal, but were not found satisfactory. Chemical treatment of the water was then investigated and sodium chromate found to give excellent results. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Full text access may be available. Click article title to sign in or learn about subscription options.
  • The varioplex-a new development in telegraphy

    Page(s): 181 - 184
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2731 KB)  

    The varioplex method of telegraphic operation provides each pair of stations connected together by it an ever- ready two-way channel for the exchange of traffic, which occupies a band width of zero when idle and of a variable width when busy, depending upon extent of simultaneous usage by other connected stations. It possesses certain advantages over, or in supplement to, other forms of manual and machine switching or repeatering. Adapted to the use of private subscribers through telemeter service, it is finding extensive application in the telegraph plant. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.