DOI:10.1049/ji-2.1942.0011

出版商:IEE    

年代:1942

数据来源: IET

摘要:

Theraison d'êtreof maximum-demand metering is first discussed and its history briefly touched on. The anomalies involved in the existing definitions and practice are pointed out. The effect of the timing of the integration period is considered, first hypothetically and then practically in the case of six actual load curves. The effect of the length of the period is then considered in the same two ways. The results are plotted and tabulated so that the effect of changes in length, etc., can be roughly predicted. The paper concludes with an experimental section embodying tests carried out by the British Electrical and Allied Industries Research Association. A number of maximum-demand meters were tested against loaded plant over certain of the load cycles, and the readings compared with the temperature rises.

DOI:10.1049/ji-2.1942.0013

出版商:IEE    

年代:1942

数据来源: IET

摘要:

Rationalization to the stage of allocation of product to particular manufacturers is rejected as impracticable in the existing organization of industry.Reduction of variety on the basis of British Standard Specifications is discussed with illustrations therefrom and with respect to certain apparatus for which no standards have been instituted.Dimensional identity is suggested for components which for practical convenience should be interchangeable.The scope for a large reduction in variety of sizes and types of cable, both flexible and armoured, is pointed out.The advantage of restriction in the number of sizes of cover glasses for flameproof lighting fittings is suggested, and the lack of agreed standards of speed in relation to output for certain types of motors is commented upon.The lack of any agreed standards of voltage is commented upon.

DOI:10.1049/ji-2.1942.0016

出版商:IEE    

年代:1942

数据来源: IET

摘要:

The use of the electrostatic voltmeter for the measurement of a.c. voltages in terms of d.c. standards is found to give rise to errors due to departure from unity of the ratio of the d.c. sensitivity of the instrument to the a.c. sensitivity. The effect appears to be due to semi-conducting films on the surfaces of the voltmeter elements, and is believed to be absent in voltmeters with working surfaces of freshly-cleaned platinum.

DOI:10.1049/ji-2.1942.0019

出版商:IEE    

年代:1942

数据来源: IET

摘要:

Circuit-breaker test plants installed during the last few years have sufficed for practically all commercial commitments except in the h.v. ranges, where high interrupting capacity is needed. For these limiting cases, variations of the direct method, and “synthetic” testing, in which the arc current is obtained from one source and the restriking voltage from a separate source, have often been advocated. In particular cases, where the tests have been confined to a single breaker of special type, such methods have been employed with apparently satisfactory results.An investigation was carried out to determine whether synthetic testing as a general means of extending the range of a test plant was economically preferable to a straight extension of the plant. This embraced a study of the requirements of the case and an estimate of the cost of the plant to meet these requirements.A circuit suitable for use with all types of breaker was devised. The restriking voltage was considered as of (1-cosine) form, rising to its peak value in times of 20–100 microsec.The results show that there is little difference in capital cost as between synthetic injection testing and the use of full plant kVA. Moreover, it is by no means certain that the synthetic method is fully equivalent to the direct test and, as clearing up this important question would entail the comparative application of both methods, it is concluded that synthetic methods cannot generally be justified economically.

DOI:10.1049/ji-2.1942.0021

出版商:IEE    

年代:1942

数据来源: IET

摘要:

The paper describes several distribution-system problems and discusses the experiences encountered in dealing with them in Shanghai. Starting with an outline of automatic protective equipment, its characteristics and operating problems, the necessity for co-ordinating all units of protection on the system is illustrated. Specific cases involving low-voltage power fuses and high-voltage “drop-out” fuses are described, and in the latter case the performance of the fuse under various fault conditions is discussed.The next problem is the testing of insulating material by the time/voltage method and its application as a means of estimating the condition of the insulation of a large number of units of equipment. Test results are given to illustrate the procedure adopted.The economical loading of power transformers is reviewed and operating data are given to support the conclusions reached. Following this, a chimney-type ventilator is described and an empirical formula, based on test results, is given.The paper concludes with a few remarks on the maintenance of equipment.

DOI:10.1049/ji-2.1942.0022

出版商:IEE    

年代:1942

数据来源: IET

摘要:

The speed/load curve of the shunt-characteristic direct-current motor worked with the increased loading constants common to contemporary design frequently departs from the legendary form. In this paper the shape of the curve which is realized in practice is stated and discussed, and instability is defined.The stabilizing and de-stabilizing influences are enumerated, and their resultant is studied as a function of the working flux.A method of approximate predetermination of the effect of the load currents in the armature is presented, and the applicability of it to the generator action of the same mechanism is pointed out.Finally, methods are discussed of suppressing excessive speed regulation with load at weak fluxes.The paper treats of machines with symmetrical main pole air-gaps; distributed compensating windings are not considered.

DOI:10.1049/ji-2.1942.0023

出版商:IEE    

年代:1942

数据来源: IET