摘要:

Attention is drawn to the fact that the majority of the published work on insulating oils has reference to their use for transformers and switchgear. The requirements for cables are briefly outlined. Experimental results are then quoted showing the bearing of the physical and electrical characteristics on the performance of the finished cable. The high importance, both thermally and electrically, of avoiding gas pockets in the dielectric of a cable in operation is indicated, and the oil characteristics necessary to secure this are stated. A sensitive method of measuring changes in the electrical characteristics is described, and a possible application to sludging tests of transformer oil is suggested.

DOI:10.1049/jiee-1.1928.0091

出版商:IEE    

年代:1928

数据来源: IET

摘要:

The basis of the true thermal rating of a transformer is the maximum temperature which the insulation will withstand without damage.In the design of a transformer to meet any specified loading conditions, calculation of the true thermal rating is necessary in order to make the most economic and efficient use of the material.Since the capacity of a transformer depends on external loading conditions, such as duration of load and temperature of cooling medium, predetermination of the thermal rating is also necessary for any combination of loading conditions that may occur in practice.Measurement of the true thermal rating while the transformer is in service is required partly as a check on the calculated rating, partly as a protection against overloading, and partly so that full and efficient use may be made of the available capacity of the transformer.The paper deals with these problems. In the first part a practical method of calculating the true thermal rating of a transformer under any given conditions of loading is developed.In the second part of the paper the measurement of the thermal rating is considered. An instrument is described which indicates, while the transformer is in service, the proportion of the maximum safe rating actually being utilized, and gives warning whenever the safe temperature limit is reached.

DOI:10.1049/jiee-1.1928.0095

出版商:IEE    

年代:1928

数据来源: IET

摘要:

Reference is made to the pioneer work of Prof. Cady and other early investigators.It is suggested that, in their practical application, quartz resonators may be almost invariably classified as “frequency standards” or “frequency stabilizers,” but reference is made to other possible uses.A distinction is drawn between the case in which the resonator is used merely to interfere with the oscillations of an electrical circuit and the case in which the resonator is employed as a means of controlling the frequency of such oscillations.Reference is made to the various modes of vibration, to the effects of temperature, and to the shapes and dimensions of the resonators commonly used.The methods of cutting and grinding are referred to, and mention is made of the sources of supply. The various methods of mounting are considered.The manner in which frequency measurements have been made is described; and a comparison is made with other types of frequency standard.A résumé is given of some of the applications of quartz resonators that have already been described in the technical Press.An account is given of the practical application of quartz resonators carried out by the authors at the Army's Signals Experimental Establishment, Woolwich. Some of the instruments containing them are described; and conclusions are drawn.

DOI:10.1049/jiee-1.1928.0096

出版商:IEE    

年代:1928

数据来源: IET

摘要:

Some methods of investigating the characteristics of down-coming wireless waves, developed at the Peterborough Radio Research Station, are described. The results of the application of these methods to wave-lengths within the broadcasting band are summarized, and their bearing on the nature of signal fading is discussed. As a detailed example of the use of these methods the observations made on the occasion of the solar eclipse on the 29th June, 1927, are given.

DOI:10.1049/jiee-1.1928.0098

出版商:IEE    

年代:1928

数据来源: IET

摘要:

The paper describes a thermionic voltmeter which can be used to measure the peak and mean values of any alternating wave-form. The instrument is provided with two scales on one dial, corresponding to peak and mean values, and a change-over switch converts the voltmeter from one reading to the other. The peak value is measured by the mean grid current of a cumulative grid rectifier. It is shown by experiment that the mean grid potential is sensibly equal to the peak value of a sinusoidal voltage, and an approximate analysis is developed by which the mean grid current can be predicted very accurately. Approximate analysis shows that the mean grid current is sensibly proportional to the peak value of any wave-form, and results are tabulated of direct tests on five different wave-forms the oscillograms of which are reproduced; at least three of these wave-forms are extraordinarily irregular. Experiment shows that the accuracy of the peak measurement is about the same as can be obtained from an ordinary oscillogram. The mean-value measurement is made by omitting the grid condenser, and the accuracy of the method is discussed analytically and substantiated experimentally. An application of the voltmeter is illustrated by curves which show the distortion produced by a 4-stage thermionic amplifier.

DOI:10.1049/jiee-1.1928.0100

出版商:IEE    

年代:1928

数据来源: IET

摘要:

After a short introduction to the subject proper the conditions of service, i.e. the loading of generators, is reviewed, and this is followed by a few notes on the control of electrically propelled ships.A short description of the types of motors used is given, and this is accompanied by a mention of a few of the more interesting points in the installations. Some of the main advantages of the electric drive are given and the author regrets that they are not being accepted. However, the author is of the opinion that conditions seem to point towards the installation of electrical equipment.

DOI:10.1049/jiee-1.1928.0102

出版商:IEE    

年代:1928

数据来源: IET

DOI:10.1049/jiee-1.1928.0104

出版商:IEE    

年代:1928

数据来源: IET