DOI:10.1049/ji-2.1947.0046

出版商:IEE    

年代:1947

数据来源: IET

摘要:

The paper develops a graphical method of determining the short-circuit current of an inductor alternator, taking into account the effect of a damping circuit which prevents oscillations of the total flux. It is shown that the short-circuit current depends mainly on the important ratio of maximum to minimum flux and on the leakage. The equivalent circuit for the inductor alternator is determined from the open-circuit voltage and short-circuit current. The ratio of these values varies owing to saturation effects, but can be taken as constant for a given excitation and independent of the load circuit.Compensation of the internal inductive reactance by series condensers for an alternator with constant and variable speed is considered, and the transient- and steady-voltage changes are investigated. The reason for the voltage drop of the fully compensated machine being many times greater than the resistive drop is given. The effect on the speed/torque characteristic of series-condenser compensation is shown.The paper explains that the damping winding increases the effective excitation for a load circuit having a lagging power factor and reduces for a leading power factor.An unusual type of instability arising when paralleling series-compensated alternators is investigated, and a remedy for this phenomenon is given.

DOI:10.1049/ji-2.1947.0047

出版商:IEE    

年代:1947

数据来源: IET

摘要:

The design of machines for medium-frequency power circuits, increasingly used in industry and in aircraft, demands a knowledge of flux-penetration phenomena as affecting both the iron losses and the utilization of the available iron section. The paper shows how hysteresis influences all important quantities, especially the eddy-current loss, the apparent flux, and the utilization factor. Theoretical expressions for these are, on certain assumptions, rather simply derived and presented in a form convenient for use in laboratories and design offices. Curves are given for this purpose, and the ranges of frequency and thickness indicated over which the influence of hysteresis on the other quantities is pronounced. Systematic collection of test results showing their departure from the theoretical values would assist in elucidating the relation of the discrepancies to the grain structure and the metallurgical history of the sheet.

DOI:10.1049/ji-2.1947.0048

出版商:IEE    

年代:1947

数据来源: IET

摘要:

This paper discusses the various factors that influence the design dimensions for an ellipsoid voltmeter to be used for the precision measurement of a specified range of high alternating voltages. Having selected the overall dimensions of the ellipsoid itself, methods for evaluating the constants of the instrument are discussed, and a method is given for determining the necessary constants for a given ellipsoid from a series of weighted measurements.The theory leading to the simple equation giving the field strength as a function of the period of the ellipsoid makes certain simplifying assumptions, and the magnitudes of the errors arising from these are considered. Where they are of the order of 0.01% or more, correction curves are given by means of which the necessary allowances can be made in any given case.The theoretical treatment is illustrated throughout by reference to a particular instrument, and it is concluded that, after its performance had been analysed on the above lines, it would give results having an estimated error of less than ±0.03%.

DOI:10.1049/ji-2.1947.0051

出版商:IEE    

年代:1947

数据来源: IET

摘要:

A calibration is given for spark-gap electrodes designed to ensure that the spark path lies in a uniform field, and it is shown that for all three sizes of electrodes investigated, covering a range of 9 to 315 kV (peak), the sparkover voltages are within 0.2% of the values given by the empirical lawV=24.22S+6.082√SkV (peak) at 20°C and atmospheric pressure of 760 mm Hg, whereSis the electrode spacing in centimetres.All observations were made with vertical gaps having the lower electrode connected to earth, and comparative data were obtained for a sphere gap with electrodes 25 cm in diameter. The effects of surrounding objects and of faulty alignment of the electrodes were determined experimentally, and on the basis of these results a number of recommendations are made, giving the limits within which the spark-over voltage is defined by the above equation.

DOI:10.1049/ji-2.1947.0052

出版商:IEE    

年代:1947

数据来源: IET