摘要:

The paper traces the development of inherent control systems in special electrical machinery over a period of more than 40 years. Starting from the concept of the 3-coil dynamo, the measures taken to make a successful constant-current d.c. generator are later shown to be applicable to constant-voltage constant-current d.c. convertors and to the control of alternator voltage, the voltage of variable-speed d.c. machines, speed, and similar applications.The development of these convertors led, in turn, to amplifying dynamos. Two basic types of convertor, and the amplifying dynamos developed from them, are briefly compared. One of them, namely the Magnicon, is treated in greater detail because of the authors' experience of this machine and because it is not very well documented in technical articles.A mathematical example of the oscillation phenomena occurring with these machines is given in the Appendices to the paper.Examples of the uses of the various machines developed cover constant-current auxiliary systems for ships, constant-voltage alternators, d. c. variable-speed machines and constant-speed control.

DOI:10.1049/pi-2.1952.0102

出版商:IEE    

年代:1952

数据来源: IET

摘要:

The object of the paper is to present the fundamental theory of natural-draught cooling towers in a form which can be applied by non-specialist engineers to the problems which arise in the design and operation of electricity generating stations.After a brief general discussion, the work of previous investigators is summarized. A convenient approximate treatment of the transfer process due to Merkel is expressed as a nomogram. The conditions under which the approximations lead to appreciable errors are defined in a form suitable for practical use.The variation of air rate through a natural-draught cooling tower with design and operating conditions is defined by an approximate equation. It is shown that routine design and performance data can be reduced to two dimensionless quantities between which correlation would be expected on theoretical grounds.By considering numerous test results in conjunction with the theoretical relationships it is shown that all tests on a given tower can be represented by a single number, termed the “performance coefficient” which is substantially independent of tower size and so offers a useful basis for comparison, interpolation and extrapolation between towers of comparable design.The application of the performance coefficient and a related quantity to the solution of practical problems is discussed and illustrated by worked examples.

DOI:10.1049/pi-2.1952.0105

出版商:IEE    

年代:1952

数据来源: IET

摘要:

The paper covers the general characteristics desirable in a battery-operated road vehicle, and describes the battery, the type of drive from motor to wheel, the motor and the control gear, small auxiliary circuits, and maintenance. Notes are added about the utility of regeneration and of motors built into the wheels.

DOI:10.1049/pi-2.1952.0108

出版商:IEE    

年代:1952

数据来源: IET

摘要:

The paper examines the economic factors which have led during recent years to a spectacular increase—in the United Kingdom more than elsewhere—in the number of electric battery road vehicles.It is shown that the cost of operation, which is examined in detail, has moved in favour of the electric vehicle as a result of the longer battery life and the greatly increased cost of labour and petrol.In view of the long life of battery vehicles, a slightly higher first cost for a model of high efficiency giving the best possible performance is economic over a long period, and a formula to compare and evaluate the performance of different models is explained in some detail. The choice of batteries for these vehicles is also discussed.The potential market for this special form of delivery transport is investigated in the light of the limitations of range and flexibility, and it is shown that, while these limitations exist, the mass-production methods of petrol vehicles can never be applicable to battery vehicles. It is suggested that a steady and increasing demand for new vehicles and replacements will call for a limited number of small efficient manufacturers able to give personal service and continuity.

DOI:10.1049/pi-2.1952.0109

出版商:IEE    

年代:1952

数据来源: IET

摘要:

The paper is a critical survey of the design of salient-pole generators in the speed range 300–1 000 r.p.m. with normal peripheral speeds of 15 000 ft/min and over, and runaway speeds of about double that figure. A Table of representative large machines is included.A review of the considerations governing the type of rotor body and the design of the pole fixing is followed by a discussion of the relative merits of laminated and solid poles and their influence on output. The design and construction of field coils is next considered with special reference to recent advances. Damper windings, ventilation and flywheel effect are also considered.The principles underlying the methods of subdividing the stator core and frame are given, and stator windings are considered in detail with particular reference to insulation, transposition and jointing.Bearing developments are reviewed, and the problem of mounting removable thrust collars on vertical shafts is discussed.The influence of various determining factors on the size of machine is analysed, and curves are included to show possible limits of output of future machines in comparison with those of the present day.

DOI:10.1049/pi-2.1952.0112

出版商:IEE    

年代:1952

数据来源: IET

摘要:

The difficulties associated with zero-drift in direct-coupled amplifiers have been overcome to a greater or lesser extent by various artifices, which have themselves often introduced disadvantages in other directions. The paper describes a design of amplifier which possesses a very low zero-drift, whilst at the same time avoiding most of the drawbacks—such as limitation of bandwidth—incurred in similar schemes. The performance is shown to be substantially that of a direct-coupled amplifier as regards frequency response, with the distinction that it may easily be designed to have zero-errors—including drift—below 1 mV (referred to the input) without the necessity for special adjustment. Phase-shifts within the range of frequencies from zero to the high-frequency cut-off can be made low enough to be neglected in closed-loop applications. The amplifier, which is of the “parallel hybrid” type, is considered to be especially applicable to high-speed servo systems, to electro-biological measurements and to precision measurements in conjunction with the cathode-ray oscillograph, as well as to precision analogue computing. The amplifier for which circuit details are given was designed for use with a high-speed pen recorder, for recording voltages over the range of frequencies from 0–90 c/s.

DOI:10.1049/pi-2.1952.0116

出版商:IEE    

年代:1952

数据来源: IET

摘要:

For blue-sensitive photographic materials the effective intensity of light from a tungsten-filament lamp is roughly proportional to the fifth power of the applied voltage. To compensate for variations in voltage, electronic timing circuits with simple circuit elements have been developed to effect exposure intervals which are inversely proportional to the fifth power of the supply voltage. With a timer of this type, provided that it is connected to the same supply as the lamp, the exposure (intensity × time) given will be substantially independent of the supply voltage.All the circuits described includeRCtiming elements, and exposures are adjusted by varying the resistance. For moderate supply-voltage fluctuations sufficient compensation can be provided by varying, in accordance with the supply voltage, either the charging potential, the bias of the relay valve or the initial charge on the condenser. Wider voltage ranges can be covered by using two of these methods simultaneously. A circuit is described which is applicable to any a.c. supply within the range 100–250 volts. The exposure time at the nominal supply voltage is continuously adjustable from 1 sec to 1 min or more, and voltage deviations of from +15 to −20% from the nominal value do not change the intensity-time product by more than ±5%.

DOI:10.1049/pi-2.1952.0117

出版商:IEE    

年代:1952

数据来源: IET

DOI:10.1049/pi-2.1952.0118

出版商:IEE    

年代:1952

数据来源: IET

DOI:10.1049/pi-2.1952.0119

出版商:IEE    

年代:1952

数据来源: IET

DOI:10.1049/pi-2.1952.0120

出版商:IEE    

年代:1952

数据来源: IET