摘要:

The paper opens with a brief review of the equipment necessary for modern X-ray work. The details mentioned in the opening paragraphs form the subjects of the sections into which the paper is divided. These subjects include induction coils, X-ray transformers, filament-heating transformers, rectification, d.c. equipment, tests and electrical measurements, switchgear and controls, fittings, and special sets.In the induction-coil section, reference is made to two new models which have some special features.In the fairly detailed discussion of X-ray transformers an attempt is made to indicate the service required from an X-ray unit and some practical features of design calculated to provide this service. Some particulars of secondary coils and bushings are included.Some causes of breakdown of the insulation between primary and secondary windings in X-ray and filament-heating transformers are cited, and means for their removal are suggested.Value tube and mechanical rectifiers are contrasted and some types of the latter are described.The need for adequate calibration and testing of X-ray plant is demonstrated, methods are proposed and suitable instruments are suggested.The provision of complete outfits in safe, totally enclosed containers, so desirable in the application of X-rays to works practice, is now possible, and details of some recent forms of portable gear are given.

DOI:10.1049/jiee-1.1929.0033

出版商:IEE    

年代:1929

数据来源: IET

摘要:

In this paper the submarine telegraph cable is discussed. The earlier non-loaded type is referred to briefly and the more recent loaded type is treated in somewhat greater detail.It is shown that, in the non-loaded cable, distortion and attenuation of signals may be reduced and speed of signalling thereby raised by increasing the section of the conductor, but a limit to this procedure is at length reached by consideration of economy and facilities for manipulation. The discovery of the alloys which exhibit high values of permeability on the application of low magnetizing forces is referred to, as is also the fact that this discovery made possible the loading of telegraph cables, with consequent great increase in speed of signalling. A description is given of the method of application of the loading material to the annealing and testing.Finally, the theory of transmission of impulses through loaded cables is briefly discussed and some details are given in regard to methods of testing during manufacture and after laying.Special reference is made to the Fanning Island-Suva (Fiji) section of the Pacific Cable (1926).

DOI:10.1049/jiee-1.1929.0037

出版商:IEE    

年代:1929

数据来源: IET

摘要:

The paper is divided into two sections and a conclusion. The first section gives the theory of the aerial as a radiator, with special reference to its ability to radiate rays parallel to the surface of the earth at its base. An account is given of experiments with different types of aerial designed to achieve this result. The reduction of the indirect ray, that is the ray producing a component of radiation at angles less than 90° to the vertical, should produce less fading of signals, and theoretical predictions are made as to the extent of such reduction. An account is given of practical tests on the fading of signals from different forms of aerial. There is some discussion as to how the desired results can be achieved in practice, having special reference both to the use of T aerials and very high masts.The second section deals with the theory of attenuation of waves having frequencies between 500 and 1 500 kilocycles per second, and gives a complete set of curves actually taken from a transmitting aerial near London.The conclusion sums up the results and gives data to enable the broadcasting engineer to specify, in general terms, the extent of service area and the effectiveness of the service to be expected, using a given power, frequency of emission of carrier wave, height of aerial and earth conductivity.

DOI:10.1049/jiee-1.1929.0039

出版商:IEE    

年代:1929

数据来源: IET

摘要:

The question of thermal transference in transformer oil was brought forward by Mr. W. Pollard Digby in 1915, † and further elaborated in a report of the I.E.E. Research Committee. ‡ Suggestions were there made for an experimental investigation to verify the conclusions reached, and the research reported herein, besides achieving this, has produced further useful information.The cooling power of three transformer oils has been investigated by means of a special apparatus, representing transformer conditions in a simplified form for experimental work.Attention has been given both to the temperature-rise of the oil and to that of the windings. It has been found that classification of oils according to temperature-rise of the fluid does not necessarily yield the same order of merit as classification according to temperature reached by the windings.The physical properties of the oils have been measured, and an attempt has been made to correlate the cooling data with these.It appears that the group of variables (ac/v) is important in both cases. Herea, candvare respectively the coefficient of expansion of the coil, its specific heat per unit volume, and its kinematical viscosity. The extreme variations of viscosity with temperature limit the precision with which this information can be applied to predict the relative performance of very similar fluids.The temperature-rise of the windings differs from that of the fluid, in that it is influenced by the thermal conductivity of the oil. Further, the influence of the thermal conductivity in this case is probably greater than the influence of the group of properties represented byac/v.The work was carried out, at the National Physical Laboratory, by Messrs. W. F. Higgins and A. H. Davis.

DOI:10.1049/jiee-1.1929.0041

出版商:IEE    

年代:1929

数据来源: IET

摘要:

The paper summarizes briefly the main precautions which should be adopted in the purchase, installation and use of electrical instruments which in a test department serve for calibrating instruments of a lower order of accuracy.The errors to which the potentiometer, dynamometer wattmeter, electrostatic voltmeter and moving-coil indicator are liable are considered, and means for eliminating or reducing such errors are pointed out.The author emphasizes the advantage of the method of discovering how errors may be produced, with the object of securing control of such errors.The conclusion is reached that, although preliminary investigations may be somewhat tedious, the result of due precautionary measures is increased all-round efficiency.

DOI:10.1049/jiee-1.1929.0044

出版商:IEE    

年代:1929

数据来源: IET

DOI:10.1049/jiee-1.1929.0047

出版商:IEE    

年代:1929

数据来源: IET