摘要:

Considerable progress has already been made in furnishing electricity supplies throughout the rural areas of Great Britain, and most of the populous centres are already supplied. Much of the remaining development work during the next few years will take place in the very sparsely populated parts of rural areas. In this development economy in capital expenditure will be of paramount importance. The paper examines the extent to which the single-phase system of distribution, both high-voltage and low-voltage, can be used with advantage in such areas for providing supplies to small villages, hamlets, farms, and other isolated premises. The electrical requirements of such communities and isolated premises are investigated in the light of practical experience gained in a typical area which is briefly described. The conclusion is reached that in rural areas, after providing a basic network on the 3-phase system for all towns, large villages and industrial consumers, there remains a considerable field in which economic development will be possible only by substantial use of the single-phase system, which is fully justified both on commercial and technical grounds.

DOI:10.1049/ji-2.1946.0108

出版商:IEE    

年代:1946

数据来源: IET

摘要:

The paper deals mainly with induction furnaces for steel melting, although some attention is given to other applications such as the case-hardening of steel. Construction of furnace bodies to avoid heating of the metal framework, and the fritting of refractory liningsin situ, are discussed. Other apparatus in the furnace circuit is described, namely high-frequency generators, methods of switching condensers and the protection of the generator. The function of series condensers and the development of earth-leakage protection in furnace circuits are discussed.The changing characteristics of furnaces due to changes in the physical properties of the charge are described, as is the effect of lining erosion.The paper concludes with a short statement on valve-operated furnaces.

DOI:10.1049/ji-2.1946.0111

出版商:IEE    

年代:1946

数据来源: IET

摘要:

Formulae are developed from Maxwell's equations of the electromagnetic field for the inductance of a single-phase system of wires or tubes arranged side by side or concentrically.Tables are given, so that the numerical evaluation of the formulae is very simple, and the formulae are shown to give values in good agreement with experimental figures.

DOI:10.1049/ji-2.1946.0115

出版商:IEE    

年代:1946

数据来源: IET

摘要:

With the increasing use of automatic control of electrical machines, and the high accuracy often required in such systems, stability problems have become increasingly important. The paper describes the analysis of some tests which have been carried out on electrical equipments in which hunting occurred. The hunting is considered as a condition of self-excitation, setting up alternating voltages and currents which are independent of the normal operation of the equipment, and are superimposed on the useful voltages and current. The way in which the hunting is sustained by self-excitation is analysed by means of vector diagrams, which give a picture of the behaviour of the circuits, and enable the factors causing hunting to be studied.

DOI:10.1049/ji-2.1946.0116

出版商:IEE    

年代:1946

数据来源: IET

摘要:

The sub-division, along various alternative discharge paths, of lightning currents produced by direct strokes to transmission towers or earth wires is determined. Theoretical solutions are further given for the tower potentials due to such strokes. The effects of varying tower-footing resistances, length of span, and number of earth wires on the magnitude and wave-shape of the currents and potentials are investigated numerically. Frequency distributions of lightning current magnitudes and of front steepnesses of the tower current are derived. Results obtained are compared with published information from field observations.

DOI:10.1049/ji-2.1946.0127

出版商:IEE    

年代:1946

数据来源: IET

摘要:

The introduction covers briefly the principal characteristics of single- and multiple-arc loads, a tentatively suggested method of electrode classification and the systems for supplying direct current to the arcs.A comparison of generators which supply single and multiple arcs shows that “copper” designs are required for single-arc generators, and “iron” designs for multiple-arc generators. Load variations in single-operator machines involve flux changes causing sluggish response and inducing e.m.f.'s in the coils under commutation. In both types of generator the m.m.f.'s of the coils under the brushes and other field forcing methods may be used to enhance response to load changes.Present design practices and standard ratings are thought to give too small single- and too large multi-operator sets. It is suggested that larger and more efficient single-operator generators and more highly rated multi-operator units of the fully compensated type will lead in both cases to overall economy.A review of the existing systems for arc supply points out some serious effects of phase unbalance and suggests that future developments lie along the lines of rotary a.c. multi-operator and d.c. single-operator generators.

DOI:10.1049/ji-2.1946.0146

出版商:IEE    

年代:1946

数据来源: IET

摘要:

Reliable equations of performance are derived for the Schrage motor by the use of tensor calculus. From these equations the centres and radii of the circle diagrams are established. Each circle is related to a certain brushseparationand a certain brushshift, which control respectively the speed and the power factor of the motor. The circle diagrams are often totally unreliable owing chiefly to wide changes in secondary resistance, a large proportion of which is brush contact resistance. The effect of this is investigated and supplemented by the calculation of two examples: in one of these the secondary resistance can be considered constant and circle diagrams can be calculated; in the other the secondary resistance is variable and the equations of performance have to be used.

DOI:10.1049/ji-2.1946.0149

出版商:IEE    

年代:1946

数据来源: IET

摘要:

This paper describes a new method of diagnosing and locating ignition faults in internal-combustion engines. Hitherto in many cases this could be effected only by the dismantling and individual inspection of the various components. The process is especially laborious and lengthy in most aircraft and tank engines, as they are equipped with screened ignition systems feeding a large number of sparking plugs, many of which are very inaccessible.In the new method, by connecting only to the primary circuit of the ignition system and by tapping off a negligible quantity of energy from one sparking plug, the performance of the ignition system under engine operation can be studied pictorially by viewing a row of stationary figures on the screen of a small cathode-ray tube. Each figure corresponds to the firing of a plug, and the figures appear on the screen in the firing order. Thus a plug can be located immediately by the position of its corresponding figure in the series. The figures undergo characteristic variations in shape according to the type of fault developed.

DOI:10.1049/ji-2.1946.0150

出版商:IEE    

年代:1946

数据来源: IET