摘要:

The paper discusses first the operating conditions and distinguishes between the different classes of service' to be furnished by stand-by plants. Subsequent sections deal with the choice of fuel, and the fields of application of oil-engine and steam plants. It is shown that only steam plants are suitable for large outputs, to which the greater part of the paper is accordingly devoted, explaining the particular requirements affectingthe auxiliary supply, the arrangement of the stations, and the turbine and boiler design, and describing the means and types of equipment which have been evolved to meet those requirements. Finally, three short sections deal respectively with instantaneous stand-by steam plants, automatic stand-by steam plants, and various recent installations of special interest.

DOI:10.1049/jiee-1.1939.0049

出版商:IEE    

年代:1939

数据来源: IET

DOI:10.1049/jiee-1.1939.0055

出版商:IEE    

年代:1939

数据来源: IET

DOI:10.1049/jiee-1.1939.0056

出版商:IEE    

年代:1939

数据来源: IET

DOI:10.1049/jiee-1.1939.0057

出版商:IEE    

年代:1939

数据来源: IET

DOI:10.1049/jiee-1.1939.0058

出版商:IEE    

年代:1939

数据来源: IET

摘要:

The paper contains a discussion of the principal features of the design of apparatus for the measurement of field strength at very short wavelengths by means of a loop aerial. The apparatus consists of a high-gain intermediate-frequency amplifier (about 1 Mc/sec) associated with a signal-frequency and frequency-change unit of constant conversion efficiency. The e.m.f. of thermal agitation in the input tuned circuit of the intermediate-frequency amplifier is used as a standard signal for setting the amplifier to a known gain. The combination of intermediate-frequency amplifier and signalfrequency unit is calibrated over its signal-frequency range by means of a radiator which gives a horizontally-polarized radiation of calculable intensity. It is shown that a single-phase, i.e. unsymmetrical, frequency-change system has certain practical advantages over biphase systems, and that this can be used without loss of the necessary balance of the aerial system, if the latter is coupled inductively through a Faraday screen to the frequency-change circuit. The detailed design of the various couplings and of the diode frequency-conversion circuit are analysed in appendices. The intermediate-frequency amplifier embodies continuously-variable gain-controls, calibrated in decibels, these components being a particular type of commercial carbontrack “volume control” which has been found satisfactory for this quantitative use. The set can be used for the measurement of field strengths down to the order of microvolts per metre at wavelengths from 7–11 metres (27–43 Mc/sec) with the frequency-change and aerial units described.

DOI:10.1049/jiee-1.1939.0059

出版商:IEE    

年代:1939

数据来源: IET

摘要:

The paper describes a direct method of measuring alternating hysteresis loss in sheet materials utilizing small disc specimens. The loss may be measured in any desired direction in the sheet on the same samples, utilizing simple apparatus. No eddy-current losses are involved in the measurement. The observed results on four electrical sheet materials are given. The Steinmetz law is found to hold approximately for the lower portion of the loss curves, and a straight-line law for the upper portion. The change is found to occur near the knee of the magnetization curve where, according to theory, the mechanism of the magnetization process also changes. A definite correspondence between the loss and magnetization curves for different directions in the sheet is found. It is concluded that hysteresis loss is a function not only of the magnetization but also of the field strength, and a qualitative explanation is given. The general relation of alternating hysteresis loss in a single crystal of silicon iron to the principal crystal directions is inferred from the observations on one of the samples. The alternating hysteresis loss is compared with the rotational hysteresis loss previously determined on the same samples. The ratio between them is found to be approximately the same for all the four materials investigated.

DOI:10.1049/jiee-1.1939.0060

出版商:IEE    

年代:1939

数据来源: IET

摘要:

The general principles which underlie the recent revision of the I. E. C. sphere-gap calibrations are given. An outline of the theory of sparkover between spheres is indicated, leading to the definition and evaluation of the “asymmetry” of a sphere-gap and to the determination of the effect ofearthing one sphere, the polarity effect, and the influence of neighbouringbodies. The correction for air density is also considered.

DOI:10.1049/jiee-1.1939.0061

出版商:IEE    

年代:1939

数据来源: IET