DOI:10.1049/jiee-1.1939.0126

出版商:IEE    

年代:1939

数据来源: IET

摘要:

For many solid dielectrics the rate of generation of heat in an alternating electric field increases approximately exponentially with the temperature. For such materials, not only the condition for a steady state and the temperature distribution in it, but also the time variation of the temperature, both when a steady state exists and when the field is above the critical field for which thermal instability occurs, is of interest and'importance. The present paper is concerned with the process of evaluating, for the transient case, the solution of the equation of heat conduction in one dimension for such a material, and gives some results.The solutions evaluated are believed to be the first calculated for a non-linear variation of generation of heat with temperature, and show a close correspondence with the results of tests on actual materials. Particularly the ultimate catastrophic rise of temperature, in fields just above the critical field which leads to breakdown, is clearly shown by the solutions. This behaviour cannot occur if the rate of generation of heat varies linearly with temperature, but these results show that it is unnecessary to postulate any other cause (such as deterioration) beyond the exponential variation of heat generation with temperature to account for it.

DOI:10.1049/jiee-1.1939.0135

出版商:IEE    

年代:1939

数据来源: IET

摘要:

For the assessment of quality of “ solid” or “ massimpregnated ” paper-insulated extra-high-voltage cables, no combination of simple tests has been found to approach in informative value an accelerated ageing test conducted at a medium over-voltage with severe cycles of conductor loading. The paper describes the technique employed by the authors in carrying out such tests and the methods used to correlate the results obtained with performance in actual service. The life-test histories of a number of experimental cables have been selected to illustrate a general discussion of the phenomena observed, and a relation between the over-voltage of the test and the life Of the cable has been established. The paper reports a programme of work that has extended over at least 8 years, and it has proved possible to demonstrate by means of a family of curves the general trend of improvement over this period. The results obtained indicate that 60-kV solid-type cables are practicable and that the possibility of 132-kV solid-type cables meeting commercial requirements cannot be overlooked. Arising from the more uniform quality of impregnation that is achieved to-day, it is probable that a majority of the breakdowns now experienced on test are determined by inconsistencies in the make-up of the solid components of the cable. It is proposed to discuss in greater detail the influence of other factors in a further paper.

DOI:10.1049/jiee-1.1939.0136

出版商:IEE    

年代:1939

数据来源: IET

摘要:

The paper deals with the development of the electrolytic condenser which is now so widely used in modern radio receivers and in amplifying apparatus.A brief historical survey is given to indicate the lines of development which have led up to the modern designs. This is followed by descriptions of the construction and chief electrical properties of the various types of condensers which are now used. These properties influence to a very great extent the manner in which the condenser can most economically and usefully be employed.Various theories have been put forward to explain the action of electrolytic condensers, but some of these do not how appear to be adequate. A critical summary is given, with an expression of views as to the most likely explanation.The manufacturing methods are treated at some length, together with the considerations which influence the employment of these condensers in various practical applications. A standardized method of test is recommended to secure uniformity in assessing their properties.

DOI:10.1049/jiee-1.1939.0141

出版商:IEE    

年代:1939

数据来源: IET

DOI:10.1049/jiee-1.1939.0145

出版商:IEE    

年代:1939

数据来源: IET

DOI:10.1049/jiee-1.1939.0149

出版商:IEE    

年代:1939

数据来源: IET