摘要:

A description is given of an all-metal oscillograph using a cold cathode and high accelerating voltage. It is capable of recording directly on a photographic film moving in vacuo at a speed of 100 metres per sec. Details are given of the construction of a vacuum drum camera and of the gland system by means of which a shaft running at 3 000 r. p. m. is brought from atmospheric pressure into a vacuum of 5 x 10−5mm of mercury.The design of the rotor (63.6 cm in diameter) and the method of fixing and retaining the film (125 mm in width) are described.The construction of the cathode-ray oscillograph is briefly outlined, and a zero-shifting device, by means of which a record 10 m long is obtained from the drum of 2 m circumference, is explained.The vacuum technique employed to obtain the low pressures required in the short times necessary for routine testing is described in some detail.Some records illustrating the capabilities and possible uses of the instrument are given.

DOI:10.1049/jiee-1.1936.0081

出版商:IEE    

年代:1936

数据来源: IET

摘要:

During the past few years a variety of applications have been found for the hot-cathode grid-controlled rectifier. In the present paper a general review is made of those industrial applications which are known to be economically possible. In order that the paper may be kept to a reasonable length and of general interest, a detailed account of the problems arising and results achieved with each application has not been attempted.A brief description of this rectifier (or thyratron) is given, together with some elementary principles which must be observed when designing circuits suitable for use with it. The grid circuit, especially, gives rise to problems and operating features probably not met with hitherto in industrial control apparatus.Though originally developed as a sensitive relay, the thyratron has now reached such a stage that it is able directly to control power of some magnitude, and thus has uses other than relaying.A Table is given showing the four main groups into which applications may be classified. Examples in each of these groups are dealt with briefly.The paper concludes with the disadvantages of thyratron control, and objections which have been raised to it. An answer can be found for most of the objections raised.

DOI:10.1049/jiee-1.1936.0084

出版商:IEE    

年代:1936

数据来源: IET

摘要:

In this paper the electric force is calculated at any point of a vertical aerial, and also the power radiated from it. It is shown that the power can always be expressed as a factor multiplying the square of the field strength at an assigned radius in the equatorial plane. This is called the “height factor”, denoted by k, and the problem is to find the height of aerial which makes this factor a minimum; for then a given direct-ray communication can be produced with the minimum power and external annoyance. The expression for the height factor is very general and is applicable to any distribution of current: it is expressed as an infinite series of certain functions of the current distribution. These functions, however, are simple ones, being the first, second, third, etc., moments of area of the current-distribution curve.The radiation resistance is calculated for a sinusoidal distribution of current, and the values agree, to within a few parts in a thousand, with those calculated in 1923 by Ballantine, who used the process of viewing the aerial from a far-distant point. It is shown that k is insensitive to the form of the current-distribution curve, provided this has a constant area. Hence it follows that the output of any aerial can be predicted with certainty provided that the value of the “metre-amperes” is known; this can be deduced if the field strength is measured accurately at a comparatively close point in the equatorial plane.The height factor is calculated for a straight aerial inclined at any angle to the ground and it is found that, for a given length of aerial, the power is always a minimum when the aerial is vertical. It follows that if a single mast of given height is available, then the most economical aerial is the straight vertical wire.A general expression is derived for the height factor of an aerial with a flat horizontal roof, of either the inverted L or the symmetrical T type. If the current distribution along the up-lead and roof is part of the same sinusoid, this expression shows that the height factor of a roofed aerial is greater than that of a vertical aerial of the same total length; and that with masts of given height it can be an advantage to omit the roof. The analysis of the roofed aerial shows that it would be economical of power to obliterate the radiation from the roof by folding up the roof. This might be done by coiling the roof into a flat spiral centred on the top of the up-lead, an arrangement which would be reminiscent of the Franklin phasing coils used in beam arrays. A given length of wire disposed in an up-lead and folded roof is never as economical of power as the same total length of wire disposed vertically, but in general a mast of given height can be used more economically if fitted with a suitable folded roof.The problem of reception is discussed briefly, and it is shown that the current distributions in reception and transmission are not the same. Finally, equations are developed for solving the current-distribution problem, and a second approximation is made to the distribution in a vertical half-wave aerial.

DOI:10.1049/jiee-1.1936.0088

出版商:IEE    

年代:1936

数据来源: IET

摘要:

The general relation between algebraic formulae and their alignment charts is explained and the use of nomography in electrical engineering is considered in particular. Therefore all the specific examples given in the paper are concerned with electrical problems. Those chosen are sufficiently typical to enable the reader to deal with most other charts he is likely to require in electrical work.

DOI:10.1049/jiee-1.1936.0090

出版商:IEE    

年代:1936

数据来源: IET

DOI:10.1049/jiee-1.1936.0091

出版商:IEE    

年代:1936

数据来源: IET

摘要:

Simple formulae are developed for the effective resistance to alternating currents of tubular conductors when used under the following conditions:—(a) Isolated conductor.(b) Single-phase system of 2 concentric conductors.(c) Single-phase system of 2 conductors of equal size laid parallel to each other.(d) Three-phase system of 3 conductors of equal size laid parallel to each other in a plane, with the middle conductor midway between the outer conductors.(e) Three-phase system of 3 conductors of equal size laid parallel to each other in triangular formation, with equal distances between conductors.In cases (a) and (b) rigid formulae are already available. The formulae developed in this paper are shown not to differ from the rigid formulae by more than a few parts in 1 000, while the reduction of labour in using the simple formulae is probably of the order of one hundredfold.In cases (c), (d), and (e), no rigid formulae are available, and the solutions put forward in this paper are the simplest and the most accurate which have yet been published. Experimental work has been undertaken to check the accuracy of the formulae and it has been found that the discrepancy between the experimental values and the calculated values is less than 3 per cent, provided that th'e ratio of diameter of conductor to spacing between axes of conductors is less than 0.85. This covers the great majority of cases occurring in practice. When the conductors are closer together than this, the errors in the formulae may be a little larger, but, even with the conductors almost touching, the greatest observed discrepancy between the experimental and calculated values of the ratio of a. c. resistance to d. c. resistance was only 6 per cent (11 per cent of the ratio of increase of resistance with a. c. to d. c. resistance).

DOI:10.1049/jiee-1.1936.0092

出版商:IEE    

年代:1936

数据来源: IET