Showing papers in "Transactions of The American Institute of Electrical Engineers in 1935"

Capacitive Excitation for Induction Generators

Abstract: Up to the present, applications of induction generators have been limited, mainly because they must be paralleled with an existing synchronous system to determine their frequency and voltage and to obtain their necessary excitation. The tests described in this paper show that an induction machine may be operated as an independent or isolated generator at a predetermined voltage and frequency, with excellent wave form, by means of capacitive excitation. Further, proper choice and arrangement of the capacitors will result in a practically flat external load-voltage characteristic.

An Analysis of the Induction Motor

Abstract: For problems involving induction motors other than the usual balanced winding type operating under steady-state conditions, a general method of analysis is necessary. In this paper, a general analysis is presented, and in particular, its use in short-circuit problems is described. The comparison between tests and calculated results indicates that the method does properly describe induction motor phenomena.

Magnetic Alloys of Iron Nickel, and Cobalt

Abstract: The unexpected magnetic propertis of certain alloys of iron and nickel discovered some 20 years ago led to a thorough study of the entire range of iron-nickel alloys. The results of this study were so encouraging that alloys of these metals with cobalt, the only other ferromagnetic metal, also were studied, as well as various alloys of these metals with small amounts of non-magnetic metals added. From the results of this extended investigation have emerged several alloys that are playing important parts in the continued advancement of electrical communication.

Breakdown Curve for Solid Insulation

Abstract: A volt-time breakdown curve for solid insulation, constructed from test data obtained with the use of square edged electrodes, is given in this paper, considerably extending the range of information available on this subject.

Pull-In Characteristics of Synchronous Motors

Abstract: The differential analyzer has proved its worth in solving various types of difficult problems, of which the determination of the pull-in characteristics of salient pole synchronous motors is typical; but even with the aid of this device it has been necessary in solving this problem to make several simplifying assumptions. The differential analyzer recently completed at the University of Pennsylvania, however, is sufficiently comprehensive in design so that few assumptions are necessary, and the major electrical transients and mechanical forces may be taken into account. Typical solutions obtained by means of this analyzer are presented herewith, together with practical pulling-into-step criteria.

The Determination of Circuit Recovery Rates

Abstract: Actual interruption of an a-c circuit depends upon the ability of the circuit breaker to prevent the re-estabishment of the arc after the current goes through zero and the arc goes out. In some circuits full voltage appears across the contacts as quickly as 40 to 80 microseconds following the current zero. This recovery rate in volts per micro-second depends upon the triple product of: the current interrupted., the normal frequency of the system, and the recovery impedance in ohms of the external circuit. The calculation of circuit recovery rates is given in this paper by presenting in curve and table form the ohmic recovery impedance, and its components, for all the practical circuits found in the field.

Capacitor Motors With Windings Not in Quadrature

Abstract: Quite often the design of a split phase induction motor is such that the so-called quadrature winding is displaced at some angle other than 90 degrees from the main winding, in which event the motor behaves differently when run in opposite directions. It is the purpose of this paper to indicate a method by which the designer can predict the performance of such a motor. While the emphasis is placed upon the capacitor motor, the treatment is applicable also to motors of other types.

Direct Measurement of Surge Currents

Abstract: Discussion and authors' closure of a paper by C. M. Foust and J. T. Henderson published in the April 1935 issue, pages 373–8, and presented for oral discussion at the instruments and measurements session of the summer convention, Ithaca, N. Y., June 25, 1935. W. W. Lewis (General Elec. Co., Schenectady, N. Y.): It may be of interest to list some applications of surge crest ammeter magnets which have been made in the past 2 or 3 years. The towers of the following lines have been completely equipped, in some cases with 4 brackets and in the remainder of the cases with one bracket per tower: The Pennsylvania Power and Light Company's 220 kv, 65 mile Wallenpaupack-Siegfried line, the Appalachian Electric Power Company's 132 kv, 65 mile Glenlyn-Roanoke line, the Pennsylvania Water and Power Company's 220 Kv, 70 mile Safe Harbor-Westport line, and the Philadelphia Electric Company's 66 kv, 14 mile Philadelphia-Chester line.

Segregation of Losses in Single Phase Induction Motors

Abstract: Methods of segregating the load losses in single phase and capacitor induction motors are presented in this paper. Segregation of losses affords a means for checking the accuracy of input-output tests, and is valuable in comparing motors of various designs.

Effects of Saturation on Machine Reactances

Abstract: The effects of magnetic saturation on the various types of reactances used in calculations on synchronous machines are considered in this paper. Saturation factors for the important constants used in transient and unbalanced load calculations are presented in curve form. These data are taken from short-circuit tests on a large number of machines. The saturation factor for transient reactance under conditions encountered in stability calculations is difficult to test directly so the test data are supplemented by theoretical calculations.

Saturated Synchronous Reactance

Abstract: It is well known that the effects of magnetic saturation are important in modifying the operating characteristics of synchronous machines. In this paper is shown a method of accurately taking into account these effects on the balanced steady-state operation of a cylindrical rotor synchronous machine by using a saturated value of the synchronous reactance. The expression for this reactance. is derived directly from fundamental principles, and its use in calculating machine characteristics accurately is illustrated on a typical steady state stability problem.

Effect of Total Voltage on Breakdown in Vacuum

Abstract: The results of a series of high voltage breakdown tests between metal electrodes in high vacuum are reviewed, with consideration of the observed inverse relation between cathode gradient at breakdown and gap length. This leads to the conclusion that the current that flows between electrodes as the conditions for high voltage breakdown are approached must involve positive ions from the anode. The deposition of anode material upon the cathode, which would occur in the event of such positive-ion emission, was found to take place. As final proof of this hypothesis, interelectrode current at constant cathode gradient was found to vary with voltage.

Armature Leakage Reactance of Synchronous Machines

Abstract: An extension of the Potier method of testing for armature leakage reactance of synchronous machines is presented in this paper, wherein it is shown that the easily tested for Potier reactance varies considerably and therefore has a limited field of usefulness. It is further shown that if the Potier reactance is measured at high values of field current, the armature leakage reactance is closely approximated and a more valuable test results.

Breaker Performance Studied by Cathode Ray Oscillograms

Abstract: Analyses of cathode ray oscillograms of circuit interruptions reveal characteristics of the circuits that are significant in the study of circuit breaker performance. While a complete analysis of such an oscillogram involves much detailed work, the study of several typical oscillograms reveals the significance of certain types of voltage variations and thus makes possible the analysis of similar oscillograms without detailed measurements. Several oscillograms made on typical laboratory circuits are presented and analyzed in this paper.

Circuit Breakers for Boulder Dam Line

Abstract: Because of its length, 270 miles, the 275 kv transmission line from Boulder Dam to Los Angeles, Calif., requires extremely high speed switching for stability. To meet the requirements, a high voltage impulse circuit breaker, extending the oil blast theory to cover a multibreak construction with double cross-blast ports, has been built. It provides over-all switching times consistently less then 3 cycles (3/60 second). Approximately 10 per cent as much oil is used as in a comparable breaker of conventional design, and only 1/10 of this is exposed to arcing. Large factors of safety are provided over and above the interrupting rating of 5,000 amperes, 287 kv, or 2,500,000 kva.

Parallel Inverter With Resistance Load

Abstract: Calculation of inverter performance and analysis of the circuit apparently have not been treated to any great extent in technical literature. This paper presents a method of calculating in terms of 2 parameters the characteristics of an inverter supplying a pure resistance load, and discusses the various modes of operation, including that in which the direct current supplied to the inverter flows in pulses.

Measurement Of Telephone Noise and Power Wave Shape

Abstract: Since the original introduction of devices for measuring or rating the wave shape of power system currents and voltages in terms of their influence on exposed telephone circuits, much additional work on this problem has been done, the results of this work are reported in this paper. In part I, a curve of relative interfering effects based upon recent studies is presented, the characteristics of a meter for measuring telephone circuit noise are described, and the results of a comprehensive series of tests on the adequacy of this meter are presented. In part II, a new telephone influence factor weighting curve is presented, and a comparison is given between results obtained by meters embodying weighting networks based upon the new and old curves.

Lightning Currents in Field and Laboratory

Abstract: A review of available data on the magnitude and effects of lightning stroke currents, supplemented by laboratory experiments to check these effects, is presented here-with. Maximum currents of 150,000 to 200,000 amperes having durations of from 40 to 100 microseconds are indicated.

Pilot Wire Relay Protection

Abstract: Recent developments in relay protective schemes, using metallic pilot channels for isolating a transmission line during fault conditions, reduce conditions, considerably the magnitude of the currents which must be handled. Schemes recently developed have many other advantages over the older pilot wire schemes being more economical to install and operate, and having excellent reliability. In addition to the advantages inherent in all pilot schemes, such as high speed tripping and absolute selectivity, the latest schemes provide indication of the condition of the pilot wire circuit at all times.

Earth Resistivity and Geological Structure

Abstract: The relation which the resistiviy of the earth's crust bears to the geological structure has been studied with the aid of many experimentally obtained data. Although the resistivity is found to vary between wide limits, and not always to be the same even for the same types of rock formation in different locations, it has been found that the variation for any particular material is within more narrow limits, and that the older materials generally have the higher resistivities. The results of the studies are of value in several types of electrical calculations.

Transmission Line Catenary Calculations

Abstract: A simple and accurate method is described for compiling stringing charts for overhead transmission lines, for either horizontal or inclined spans. All calculations can be carried out with a 20 inch slide rule, and no tables of functions are required other than those included in this paper. The procedure is the same for horizontal and for oblique spans. Moreover, no loss of accuracy is suffered as the inclination of the span is increased. The final result is obtained by means of a graphical solution which, in principle, is based upon the Thomas chart.

Transient Voltages on Bonded Cable Sheaths

Abstract: Field experience and tests show that unexpectedly high transient sheath voltage occur during the switching of charging current in single-conductor cable-type bus leads and in underground single-conductor power transmission cables bonded to eliminate sheath losses. No sheath troubles from these voltages have been found. Theoretical analysis of these voltages is presented together with suggested methods for protection of equipment, when the latter is necessary.

Dielectric Strength of Mineral Oils

Abstract: The correlation of the pressure and temperature effects in determining the dielectric strength of mineral insulating oils is considered in this paper. The effect which gas dissolved in the oil has on the dielectric strength of the oil is shown by experimental results of tests on the effect of temperature and pressure. Based upon these results, simple formulas for expressing the dielectric strength of oil are obtained.