摘要:

Position-control servo mechanisms are frequently required to operate smoothly through a very wide range of speeds; the limitation to smooth running at creep speeds is invariably imposed by the non-linear friction in the bearings, gears, etc., associated with the output shaft. The object of the paper is to outline two methods of investigating the effects of static and Coulomb friction on the minimum smooth-running speed of a position-control system. The first method follows closely some recent work on non-linear mechanics and is particularly suited to the non-linear friction problem because it provides a qualitative picture of the behaviour of a system; the method has been applied to a simple mechanical filter-system. The second method uses the differential analyser to solve the non-linear differential equations describing the behaviour of the system. The use of the differential analyser for this problem presents some interesting features, and the running procedure of the machine for the case of the mechanical filter has been described in some detail.Some results are presented which were obtained with the differential analyser in connection with the behaviour of a typical automaticfollowing radar servo-system incorporating a metadyne-controlled motor at creep speeds. It is pointed out that, notwithstanding the rather special and complex nature of the system for this example, it is probable that the general nature of the results will not differ appreciably when other systems are used.

DOI:10.1049/pi-2.1951.0092

出版商:IEE    

年代:1951

数据来源: IET

摘要:

The paper deals with the design of surge diverters which consist of one or more enclosed spark-gaps in series with a column of non-linear resistors. The factors which affect the sparkover voltage of the gaps and their ability to interrupt follow-current are illustrated by consideration of a variety of designs of gap of different complexity. Methods of distributing the voltage between a number of seriesconnected gaps are considered. The characteristics of silicon-carbide non-linear resistors are discussed, and some observations are made on the mechanism of sparkover and puncture at large surge currents. Surge diverters are classified as rural-, line- or station-type according to the surge current which they will safely carry, and performance figures and curves are given for each of the three types.

DOI:10.1049/pi-2.1951.0096

出版商:IEE    

年代:1951

数据来源: IET

摘要:

The author outlines work done in the first year of nationalization in one of the fourteen supply areas with regard to estimating potential load; plans designed to meet these loads, dealing with the primary, secondary and tertiary networks separately; the amount of standardization that is aimed at; and the methods used in carrying out the work.

DOI:10.1049/pi-2.1951.0099

出版商:IEE    

年代:1951

数据来源: IET

摘要:

In 1946, the author read a paper before this Institution on the “Electrical Control of Dangerous Machinery and Processes.” A little earlier, Mr. H.A. Hepburn had read a paper on “The Fencing of Dangerous Parts of Machinery” to The Institution of Mechanical Engineers, and he suggested to the author that the interlocking of such guards and fencing would prove an appropriate subject for a useful continuation of both papers.The present critical study, which is a development of one Section of the 1946 paper, arises from that suggestion; its subject matter is sufficiently indicated by its title, and it is only necessary to add that, in it, an attempt has been made to deduce a number of guiding principles of design and not to describe particular mechanisms in detail.

DOI:10.1049/pi-2.1951.0102

出版商:IEE    

年代:1951

数据来源: IET

DOI:10.1049/pi-2.1951.0105

出版商:IEE    

年代:1951

数据来源: IET

DOI:10.1049/pi-2.1951.0106

出版商:IEE    

年代:1951

数据来源: IET

摘要:

Work on the voltage characteristics of polythene cables has been described in a previous paper; the present paper gives the results of further studies. Factors contributing to the breakdown of polythene cables have been investigated, and tests on cables have been supplemented with a similar series of tests on artificially produced voids. Voltage/life characteristics of cables with solid dielectric and a single non-stranded conductor have been examined, and voltage ratings, based on experimental work, are proposed for alternating and direct stresses.

DOI:10.1049/pi-2.1951.0107

出版商:IEE    

年代:1951

数据来源: IET

摘要:

It is pointed out in the paper that the performance of polyphase synchronous machines with balanced loading can be predetermined reasonably satisfactorily by several well-known methods, but that very little attention has been given to the calculation of performance with unsymmetrical loading, when normal values of saturation apply.The paper outlines a simple analysis of a synchronous machine for the latter conditions—i.e. when carrying unbalanced currents of normal magnitude. It is shown how the standard methods, used for performance calculations with balanced operation, may be adapted for unbalanced conditions.The test results confirm the validity of the suggested technique.

DOI:10.1049/pi-2.1951.0108

出版商:IEE    

年代:1951

数据来源: IET

摘要:

In large electrical machines, such as alternators and transformers, that include sheet-steel laminations in their construction, it is essential to insulate the core laminations from one another to reduce eddycurrent stray loss. One method is to varnish the sheets after stamping, before assembly in the core. The need for developing good varnishing technique demands satisfactory measurement of the insulation. One convenient method is to measure the electrical resistance of the insulating film, and this can be done in several ways. The paper attempts to analyse the fundamental problem of the measurement, deduces that it is essentially a statistical problem, and suggests a method by which it may be solved. The paper then proceeds to discuss the possibility of correlation between experimentally measured values of resistance and observed stray losses in completed machines. There is also some consideration of other relevant factors, such as temperature, pressure, and the nature of the plate surface.

DOI:10.1049/pi-2.1951.0109

出版商:IEE    

年代:1951

数据来源: IET

摘要:

The distribution of the magnetizing force inside a ferromagnetic lamination subjected to a.c. magnetization at its surface is determined by the application of Southwell's relaxation methods, on the assumption that the static (or d.c.) characteristics of the material are applicable directly at any point in the lamination under dynamic (or a.c.) conditions. The flux and eddy-current distributions and the “dynamic hysteresis loop” are then evaluated. The alternative conditions of sinusoidal magnetizing force (at the surface) and sinusoidal total flux are considered for a frequency of 50 c/s. Consideration is also given to higher frequencies of operation when the surface magnetizing force is of sinusoidal waveform.

DOI:10.1049/pi-2.1951.0112

出版商:IEE    

年代:1951

数据来源: IET