DOI:10.1049/jiee-1.1930.0209

出版商:IEE    

年代:1930

数据来源: IET

DOI:10.1049/jiee-1.1930.0210

出版商:IEE    

年代:1930

数据来源: IET

DOI:10.1049/jiee-1.1930.0211

出版商:IEE    

年代:1930

数据来源: IET

摘要:

In connection with the driving of a wireless direction finding rotating beacon it was found necessary to devise means of controlling a motor so as to obtain accurate constancy of speed over wide ranges of mains variation.In the first instance experiments were made with a governor such as that used in the Baudot printing-telegraph system, but it was found that it did not absorb sufficient power to enable it to be used on the direction-finding rotating beacon. With a view to diminishing the amount of power that need be absorbed by the governor, an electric circuit arrangement for the supply of power to the electric motor used to drive the beacon was devised, and finally an eddy-current governor with clock control was designed. The clock control is intended to enable two beacons to be run with alternate periods of transmission, without the possibility of serious overlapping of these periods. The accuracy of the governor control is of the order of 0.05 per cent with 30 per cent mains-voltage fluctuations, while the clock control limits the cumulative error to less than 1 degree of azimuth.

DOI:10.1049/jiee-1.1930.0212

出版商:IEE    

年代:1930

数据来源: IET

摘要:

The problem of finding a light alloy of aluminium which will satisfactorily eliminate the steel core for overhead electrical conductors is of importance at the present time. The ½ per cent magnesium alloy, under the name of Aldrey, is being used on the Continent without steel core, and the present paper is concerned with its exposure to London atmosphere. The conductors are in the form of wires and have been exposed on the roof of King's College since October,1928. The variations in their electrical and mechanical properties have been studied with special reference to type of corrosion and mechanical stress has proved beneficial so far as variations in tensile properties are concerned, it has had but a small effect upon electrical conductivity. An account is given of experiments which have been made to explain the reason for the beneficial results obtained. The paper refers to published work on the atmospheric exposure of light nickel alloys, duralumin, and high-purity aluminium, and comparisons with the present experiments have been made and discussed.

DOI:10.1049/jiee-1.1930.0213

出版商:IEE    

年代:1930

数据来源: IET

摘要:

This report gives directions for the employment of a neon lamp as a substitute for an oscillograph in the detection of transient low-current arcs between the case and poles of metal-clad fusible cut-outs operating under short-circuit conditions. Such arcs can only be detected by special means, but previous tests have shown that they are the precursors of others of much greater magnitude and duration when the short-circuit current is increased, and invariably lead to complete destruction of the cut-out.The characteristic of the neon lamp of which advantage is taken is that there is a difference between the minimum voltage which will cause the lamp to glow and the value (about 20 volts less in commercial lamps) to which the voltage may subsequently be lowered before the lamp is extinguished. In the method described herein, the transient voltage across a resistance arising from the passage of a transient arc causes the lamp to glow, and in virtue of the above characteristic it then remains glowing indefinitely although the arc has ceased.Directions are given for obtaining maximum sensitivity (for present purposes) from any given lamp, and a simple method of selecting the most sensitive lamp from a stock is described. It is shown that the ordinary commercial neon lamp costing a few shillings can readily be made to detect transient arcs of about 20 amperes flowing for 0.002 sec., which is all that is required in practice, while a similar lamp specially selected by the methods described responded to the passage of a current of 3 amperes for 0.0005 sec.The only drawback to the ordinary commercial neon lamp is that, owing to impurities in the gas, etc., its characteristics may vary with time, although in the tests no appreciable variation was noted after 100 experiments. Constant characteristics can be obtained by suitable precautions in manufacture, and the General Electric Co.'s. Research Laboratories have kindly signified their willingness to make up special lamps of this type for the above purpose at a cost of less than 20s. each.

DOI:10.1049/jiee-1.1930.0214

出版商:IEE    

年代:1930

数据来源: IET

摘要:

The classical mathematical method of calculating the wave-form of rectified currents is applicable to rectifiers whose volt-ampere characteristic consists of two interesting straight lines. It is based on the observed fact that there is for each rectifier a conducting phase and an insulating phase. If the characteristics for each are linear, the differential equations are linear and can be solved for each separetely. The discontinuities between the two conditions are bridged by transient terms in the integrated equations. To evaluate the harmonics, Fourier's theorem is necessary. Even for the simplest circuit the labour of calculation is very great, although the result is mathematicallly exact.A new method is proposed which treats the rectifier characteristic as a continuous curve having an equationE=f(I)In every part of the circuit except the rectifier the harmonics are independent, since the coefficientsL.R.Care assumed constant. It is therefore an easy matter in any given circuit to calculate each harmonic ofEin terms of the harmonics ofI. The voltage and current must, however, at every instant of time satisfy the characteristic equation of the rectifier, and this leads to sufficient equations for a solution by successive approximation. The method is applicable to cases of biphase rectification, and, like the classical method, has its simplest application for ideally perfect rectifiers having a characteristic equationEI=0The paper shows the method of reducing the equations to tractable form for solution by successive approximations, using the algebra of plane vectors, and it is shown by means of a numerical example how the approximations converge on the true value deduced by the classical method.

DOI:10.1049/jiee-1.1930.0215

出版商:IEE    

年代:1930

数据来源: IET

摘要:

This paper deals with the mechanical arrangement of the locomotive, and with the electrical gear in so far as it affects the mechanical design. The influence of the mechanical arrangement on the riding of the locomotive is briefly considered. Some of the most important driving systems are described and criticized, and a short explanation of the causes of trouble in side-rod drives is given.

DOI:10.1049/jiee-1.1930.0216

出版商:IEE    

年代:1930

数据来源: IET

DOI:10.1049/jiee-1.1930.0217

出版商:IEE    

年代:1930

数据来源: IET