摘要:

The high efficiency of mercury-arc-rectifier equipments would appear to make their use desirable on winder drives, on which efforts are continually being made to reduce hoisting costs. After outlining the requirements of a winding engine, the paper briefly describes a.c. and Ward Leonard drives, discusses their advantages and disadvantages, and compares them with a rectifier drive. The advantages of the latter led to the installation of such an equipment at Monk Bretton No. 3 Shaft, and the various rectifier connections and the methods of changing from rectification to inversion are considered. Various aspects of grid control and transformer design are discussed, and some rectifier faults are described, together with the protection provided against such faults. The winder is provided with closed-loop speed control and the system used is described. A comprehensive series of tests was carried out on the installation and the results obtained are illustrated.

DOI:10.1049/pi-a.1958.0023

出版商:IEE    

年代:1958

数据来源: IET

摘要:

The paper states briefly the reasons for earthing low- and medium-voltage distribution systems and equipment. Reference is made to various methods of earthing and to the main difficulties encountered in putting them into practice, particularly in rural areas.The main objects are to describe the development of the system known as protective multiple earthing, to show the advantages of this system and to explain the reasons for its adoption on a wide scale in the rural zones served by the North Western Electricity Board.The experience of the Board with the p.m.e. system from 1949 onwards is described.

DOI:10.1049/pi-a.1958.0026

出版商:IEE    

年代:1958

数据来源: IET

摘要:

The paper describes an extensive investigation into the design of transformers with the aid of a high-speed digital computer. A general programme has been developed covering a range of transformers from 30 to 210 MVA, and has been tested for a wide range of designs within these limits. The subdivision of the process of design and its translation into a form suitable for a digital computer are described. Basic details of particular sub-routines are given to illustrate the problems of logic and arithmetic encountered. The techniques needed to control the design process within the computer are discussed, with special reference to the organization of data. A detailed description and derivation are given of the method used to obtain convergence to specified design characteristics without intervention by a designer. The results of several investigations concerned with the effect of changes to certain design parameters are included.

DOI:10.1049/pi-a.1958.0029

出版商:IEE    

年代:1958

数据来源: IET

DOI:10.1049/pi-a.1958.0032

出版商:IEE    

年代:1958

数据来源: IET

摘要:

The paper surveys the progress in switchboard control of stage and television lighting which has been made in the past 25 years. The various types of dimmer which form the basis are outlined, with particular reference to their remote control. The methods of co-ordinating control, using particular forms of levers and grouping aids, such as master selection and presetting, are described.Details of the application of organ-console techniques to the ‘playing’ of light are given, together with reasons for a preference for electromechanical dimmer systems rather than the American all-electric dimmer or the Continental electro-mechanical desk. All three systems are described.

DOI:10.1049/pi-a.1958.0033

出版商:IEE    

年代:1958

数据来源: IET

摘要:

The paper describes the experimental work and results of a study of the heat-transfer properties of cooling ducts in transformer coils under natural convection. The data for layer windings of various vertical duct sizes and coil heights are generalized in terms of empirical copper-to-oil temperature gradients. Consideration of the vertical coil leads to a method of treating an assembly of disc coils individually, and it is shown that the individual disc-coil variables are represented conveniently by a correlation type of formula. Finally, it is indicated how the data may be used to predict the hot-spot temperature of a transformer in service.

DOI:10.1049/pi-a.1958.0034

出版商:IEE    

年代:1958

数据来源: IET

摘要:

In an effort to improve operating and technical characteristics and to eliminate some of the difficulties experienced when semi-skilled or unskilled persons are employed as drivers of electric locomotives in South African mines, an investigation was made to develop an improved, simple drive system having as many foolproof features as possible.A drive consisting of two compound-wound d.c. motors coupled differentially to the road wheels through an epicyclic-gear unit was examined and found to meet the requirements. Subsequent tests on a 4½-ton experimental locomotive confirmed the features expected, and demonstrated in addition numerous useful characteristics not previously available on small locomotives.Ease and sensitivity of control, electric braking at any speed, exceptional manoeuvrability, inherent limitation of both tractive and braking efforts to prevent wheel-slip and skidding, virtual elimination of sparking at the controller contacts, limitation of motor loading and line current for any combination of controller position, drawbar load and speed, inherent automatic acceleration and maximum power economy at any speed and load are some of the more attractive features.The paper describes the drive and explains its basic characteristics by mathematical analysis.

DOI:10.1049/pi-a.1958.0035

出版商:IEE    

年代:1958

数据来源: IET

摘要:

The problem of circulating corrosive liquids assumes a major importance in nuclear-engineering practice, where the standards of safety and reliability which are imposed demand sealed circulating systems. One method employs a completely enclosed centrifugal pump driven by a squirrel-cage induction motor in which the rotor is separated from the stator by a thin cylindrical corrosion-resistant shell which is situated in the air-gap of the machine and effectively forms part of the retaining wall of the circulating system. A precise assessment for design or development purposes depends on a knowledge of the power losses in the stationary shell and it is a solution of this eddy-current problem which is developed in this paper.Arguments more appropriate to field theory than to circuit theory lead to a classical boundary-value problem which takes into account the nature and thickness of the shell and the length of overhang, and provides formulae for current densities, flow lines and dissipated power in terms of ordinary machine parameters and the dimensions and electrical constants of the shell. Theoretical and practical results are compared and shown to be in close agreement. Some of the graphical results display a pronounced slot effect and suggest methods for making a more detailed investigation.The theory can be extended to correspond to a composite shell of complex structure and it has some bearing on the principles employed in drag-cup motors, to which it could be applied.

DOI:10.1049/pi-a.1958.0036

出版商:IEE    

年代:1958

数据来源: IET

摘要:

The paper reviews the methods by which the mean, r.m.s., or peak values of voltages ranging from 10 kV upwards may be measured by indicating or recording instruments to an accuracy within about 1%. Most of the methods use either a low-range high-impedance voltmeter or cathode-ray oscillograph in conjunction with a voltage divider or a milliammeter in series with a high impedance.Voltage dividers suitable for use with direct, alternating and impulse voltages are considered, and, amongst the measuring instruments, the diode peak voltmeter is discussed in some detail. High-range electrostatic voltmeters are also considered.It is concluded that there are always at least two different methods by which a particular type of voltage may be measured.

DOI:10.1049/pi-a.1958.0037

出版商:IEE    

年代:1958

数据来源: IET