DOI:10.1049/ji-2.1946.0049

出版商:IEE    

年代:1946

数据来源: IET

摘要:

The forces and stresses set up in transformer windings and their clamping structures, as the result of external or internal short-circuits or of switching operations, are considered in detail.Various arrangements of windings and tappings in large power transformers are described. Points at which particularly high mechanical stresses occur in concentric windings are discussed in detail. Axial forces between the top and bottom halves of each winding or between different windings are responsible for bending stresses in turns near the ends or adjacent to gaps in the windings, for compressive stresses in the body of the winding, and for tensile and compressive stresses in the clamping gear. Radial forces produce tensile stresses in the outer and buckling stresses in the inner winding. Such stresses are more pronounced in coils adjacent to the main leakage duct. The excessive mechanical stresses which can be caused by internal electrical breakdowns are discussed. The mechanism of cumulative shrinkage, the loss in clamping pressure due to switching stresses and thermal cycles, and the danger of subsequent movement of the windings causing abrasion of the insulation and final electrical breakdown, are considered in detail. A rule is given for the minimum clamping pressure that should be maintained within the windings. Readers interested in the mathematical treatment of the subject-matter are referred to E.R.A. Reports, Refs. Q/T101, 103, 105 and 106, in which quantitative expressions are derived for the maximum values of currents, forces and stresses which can occur in the windings. Certain statements made in this paper on the merits of various forms of design represent the personal opinion of the author. They do not necessarily express the official opinion of the E.R.A.

DOI:10.1049/ji-2.1946.0057

出版商:IEE    

年代:1946

数据来源: IET

摘要:

The paper examines the policy applied to-day to electrical installation work, from the inception of the scheme in the client's mind o the handing over of the completed installation to his maintenance organization.Suggestions are made as to where these fall short of requirements as regards the position of the electrical engineer, and as to where procedure might be improved in order to bring the electrical engineer into his rightful place in relation to all technical branches involved in building and civil engineering construction work to-day.In conclusion, it is suggested that the architect's organization usually set up for the execution of his commissions is open to much improvement and that the electrical contractors engaged on such works should not necessarily be nominated as sub-contractors and left under the direct control of the main contractor's agent. It is suggested also that the existing practice in regard to contracts could be improved, and that more attention should be given to the site organization responsible for supervising the installations in question. Work carried out must be treated with greater continuity from the first stages of design to the final handing over than has been common in the past.

DOI:10.1049/ji-2.1946.0060

出版商:IEE    

年代:1946

数据来源: IET

摘要:

Partly from theoretical considerations, but mainly from practical data, an empirical formula is derived giving the approximate weight of any tower in terms of its height and maximum working overturning moment at the base. The tower weight above ground line is shown to be satisfactorily represented bykH√Mtons, whereHis the overall tower height above ground line, in feet;Mis the overturning moment at ground line, in thousand lb-ft; andkis a “constant” which varies within an extreme range of about 0.0014 to 0.0029 throughout the whole series of towers; most towers havekvalues well within this range.The towers investigated covered ranges of about 16 to 1 in height, 3 000 to 1 in overturning moment, and 1 200 to 1 in tower weight.Design factors which explain variations in the “constant”kare discussed at some length on a qualitative basis.It is shown that an economic value for the base width of any tower is in the neighbourhood of 0.5√Mft.On the assumption that, for any given general type of tower, the total erected cost may be regarded as proportional to the aboveground weight, the tower-weight formula,kH√M, can be used with convenience and reasonable accuracy for a wide field of cost estimations, especially those involving comparisons of a number of alternatives of a generally similar nature.Such investigations include the following:Ordinary transmission lines: (a) Economic span lengths. (b) Relative costs of lines for different voltages, conductor sizes and conductor materials. (c) Number of circuits. (d) Number and height of earth conductors. (e) Abnormal wind and ice loading assumptions and/or actors of safety. (f) Different clearances between conductors and ground. (g) Suspended auxiliary cables. (h) Hypothetical “dogleg” lines. (j) Hypothetical “super e.h.v.” lines.Navigable river crossings: (a) General layout. (b) Clearance to high water; Air Ministry height restrictions. (c) Span lengths and river bank configuration. (d) Foundation conditions. (e) Number of circuits. (f) Long spans; economic conductor. (g) Narrow waterways; economic number of towers. (h) Terminal-type crossing towers; economic conductor tension.

DOI:10.1049/ji-2.1946.0063

出版商:IEE    

年代:1946

数据来源: IET

DOI:10.1049/ji-2.1946.0066

出版商:IEE    

年代:1946

数据来源: IET

摘要:

This paper forms one of a series of papers on standardization initiated by The Institution. The objects of standardization and its resulting benefits have been frequently stated and reviewed in recent years, but still form the subject of debate. They comprise improved manufacturing efficiency, shorter delivery times, more economic production, the reduction of design and drafting work with conservation of technical man-power, and the stocking, interchangeability and reduction of spares.The main factors as affecting both user and manufacturer are reviewed in order to ascertain their ideas of what should and can be done. The problem and possibilities are closely related to the organization of the transformer manufacturing industry.Schemes for the standardization of electrical machinery involve three main factors: supply-system requirements, fundamental dimensions and constructional features, and detailed design. The transformer problem does not differ in kind from that relating to other classes of electrical apparatus, and the present analysis of the transformer problem follows broadly similar lines.Standardization of supply-system requirements, including ratings and electrical performance, is a natural precursor to dimensional and design standardization. Although the subject of ratings and performance is already covered by the relevant B.S. specifications, certain matters, mentioned in the paper, require reconsideration and amplification when those specifications associated with transformer practice come up for revision.The problem of dimensional standardization is examined, and suggestions are made for the standardization of fundamental dimensions to effect interchangeability of different makes of transformers and fittings, without individual manufacturers having to forgo their own detailed designs and manufacturing techniques.Some examples are given illustrating dimensional standardization already accomplished.Detailed design standardization would only be feasible or necessary under a scheme of manufacture involving allocation of work or centralization of manufacture.It is suggested that efforts should be made towards achieving effective standardization of supply-system requirements to suit operating conditions, and that schemes should be considered and planned jointly by the interests concerned, to secure some measure of dimensional standardization of distribution transformers and medium-size power transformers and their principal accessories.

DOI:10.1049/ji-2.1946.0067

出版商:IEE    

年代:1946

数据来源: IET