摘要:

The use of the electrolytic tank as an analogue method of solving field problems has long been known, but many practising engineers and teachers may be unaware of the various applications of the method, and of its value as an engineering tool and in engineering education. The purpose of the paper is to present qualitatively, and in nonmathematical terms, certain of the field problems which may encountered in electrical-engineering design and which may be solved conveniently with the aid of simple models in an electrolytic tank.The examples are drawn mainly from the electric and magnetic field problems in electrical engineering, but indications are also given of the application to mechanical engineering. It is hoped that these examples and explanations of the various analogies will give the engineer a clearer physical picture of electric and magnetic field configurations, and that they will stimulate the interest of teachers and students in engineering colleges, and perhaps indicate useful avenues of research and wider application of the technique.

DOI:10.1049/pi-2.1954.0080

出版商:IEE    

年代:1954

数据来源: IET

摘要:

The paper discusses the experience gained and the results of experiments performed whilst endeavouring to obtain satisfactory performance from electrostatic precipitator plant.The principal factors determining drift velocity in precipitators are discussed. A simple approximate relation for the field strength in a parallel-plate horizontal-flow precipitator is developed, based on that generally accepted for a wire-in-cylinder precipitator unit.Comprehensive expressions are introduced for calculating the theoretical performance of precipitators under conditions of nonuniform gas flow and with dust of mixed composition. It is shown that individual drift velocities for different particles may be determined from appropriate experimental observations.The suggestion that pulverized fuel dust is composed largely of two distinct types of particles, one wholly ash and the other coal minus volatiles, i.e. coke, is discussed. Evidence, principally from South African sources, is put forward to support this suggestion.The effective drift velocities obtained in practice for plants operating on Natal duff coal are calculated for a given field strength and are compared with those measured elsewhere. Separate drift velocities for average ash and coke particles are given, and the former are shown to have higher useful drift speeds than the latter.It is shown that, as predicted in theory and as previously proved under laboratory conditions, the drift velocities of particles of the sizes encountered in practice do, in fact, increase with the particle diameter, given a constant composition.Finally, notes are included on the interpretation of test data in order to locate and correct the more common sources of poor performance of precipitators.

DOI:10.1049/pi-2.1954.0083

出版商:IEE    

年代:1954

数据来源: IET

DOI:10.1049/pi-2.1954.0086

出版商:IEE    

年代:1954

数据来源: IET

摘要:

The utilization of low-grade products in the pithead power plants of the Lorraine coalfield entails certain special arrangements. This study deals with these arrangements, and, in particular, with the problems set by the transport, preparation and drying processes as well as by the collection and disposal of coal dust.

DOI:10.1049/pi-2.1954.0087

出版商:IEE    

年代:1954

数据来源: IET

摘要:

A theoretical investigation of the relative magnitudes of the phase magnetizing currents and of the wattmeter readings when measuring iron losses in a three-core transformer is given. The effect on the accuracy of the observed iron losses of phase-angle errors in the wattmeters is examined. The magnitude of possible errors is shown by numerical example.

DOI:10.1049/pi-2.1954.0090

出版商:IEE    

年代:1954

数据来源: IET

摘要:

The instrument measures the hysteresis loops of magnetic materials and plots the curves directly by pen on paper. The measurements are made under virtually zero-frequency conditions, the period of the cycle being nearly one minute. The magnetic flux is detected by a search coil on the sample, the e.m.f. being amplified and integrated by avariable-speed motor on the plotting table, whereby the displacement of the pen is a measure of the magnetic induction.The instrument is calibrated in terms of voltage and time, which offers good absolute accuracy. Comparative experiments against afixed mutual inductance and a Hibbert magnetic standard show agreement within about 1%. The equipment is intended to give measurements equivalent to those obtained with a ballistic galvanometer, but with greater convenience; a comparison with a wide rangeof samples shows agreement within ±1%, with certain exceptions.In Appendices are given (a) a circuit of a sensitive servo system used in plotting the magnetizing current, incorporating a magneticinverter; (b) considerations for the design of a galvanometer to berelatively unaffected by mechanical disturbances; and (c) the design of an optical system for a galvanometer-photocell amplifier giving maximum optical efficiency.

DOI:10.1049/pi-2.1954.0091

出版商:IEE    

年代:1954

数据来源: IET

摘要:

The paper discusses the special features of a 275-kV bank of single phase transformers developed for use in a new research station for proving high-power circuit-breakers.After a review of the specification for the transformers, the basic design is dealt with in some detail. The abnormally low impedance, which is constant on all voltage ratios, was achieved by adopting ashell-type construction with interleaved windings; the special measuresused to produce this winding design for an insulation level of 1250 kV(full-wave impulse) are examined.Some of the manufacturing techniques are described, and, in particular, reference is made to radiography used as an inspection tool to check the totally shrouded windings. The drying and impregnating processes are discussed, and a typical log of relevant data is reproduced. Finally, impulse-voltage test results on sample windings and the finished transformers are examined.

DOI:10.1049/pi-2.1954.0093

出版商:IEE    

年代:1954

数据来源: IET

摘要:

Measurements have been made of the direct and impulse breakdown voltages of gaps between spheres 2 cm in diameter, as recommended in B.S. 358: 1939. Discrepancies are found to exist, and suggestions for a revision of this Standard are made.

DOI:10.1049/pi-2.1954.0094

出版商:IEE    

年代:1954

数据来源: IET

摘要:

A special electron-optical system for producing a low-energy beam, as far as possible only in the absence of a magnetic field, is described. Its use for measuring both the strength of d.c. magnetic fields relative to a static reference field, and the relative strengths of time-dependent magnetic fields, with the aid of the voltage pulse which it produces at field zero, is described. The various factors affecting the amplitude and width of such pulses are discussed, and quasi-static measurements are given in support of the conclusions derived from a simple theoretical analysis of such factors. The operation of such an instrument in timedependent magnetic fields, such as those found in particle accelerators like the betatron and electron-synchrotron, is briefly discussed.

DOI:10.1049/pi-2.1954.0095

出版商:IEE    

年代:1954

数据来源: IET

摘要:

A circuit is described for the precise temperature control of the oven of a quartz-crystal frequency standard. A temperature-sensitive bridge of copper and manganin resistors is used as the amplitude control of an oscillator, power from the oscillator heating the oven. It is shown that the temperature of an isothermal oven is maintained independent of ambient temperature and depends only on the gain of the maintaining amplifier. An application of the thermostat is described in which the oven temperature of about 50° C is maintained within ±1 millideg.

DOI:10.1049/pi-2.1954.0096

出版商:IEE    

年代:1954

数据来源: IET