摘要:

Considerable progress has been made with electrical heating in recent years. The higher cost of electrical energy as compared with the cost of solid or liquid fuels is compensated by the advantages of cleanliness, convenience and efficiency.The authors advocate the more extended use of electrical heating by adopting thermal storage, thus enabling energy to be used during off-peak hours. They contend that such a system is economical to operate, and they show that, for large buildings, electrical heating can compete with systems employing other forms of fuel.

DOI:10.1049/jiee-1.1930.0065

出版商:IEE    

年代:1930

数据来源: IET

摘要:

The paper deals with a method—which so far has not received the attention of engineers—of converting electrical energy into heat energy. The method is based on the general principle that the efficiency of the heat engine working in the normal cycle is given by(T1— T2)/T1, whereT1is the high temperature andT2the low, and that the heating efficiency of a reversed-cycle heat engine is given byT1/(T1— T2). The reversed-cycle heat engine (or heat pump) is described, and it is shown both from theoretical considerations and from practical tests on refrigerating plant that where heat at a comparatively low temperature is required, heating efficiencies of the order of from 300 to 500 per cent or even more may be obtained, the heating efficiency being defined as the ratio of the heat produced by the heat pump to the heat equivalent of the electrical energy consumed.The application of this principle to the heating of buildings and for such purposes as the heating of public baths is discussed, and estimated figures for a public-bath installation are given. The paper concludes with a description of experiments which the author has been carrying out during the past 2 years, and which have demonstrated the soundness of the general principles on which the heat pump is based.

DOI:10.1049/jiee-1.1930.0066

出版商:IEE    

年代:1930

数据来源: IET

摘要:

The paper deals in a general way with the whole field of instrument transformer work, and in a more extensive manner with certain developmets and views for which the authors are more particularly responsible. Among these are the following:—Current Transformers.— (i) Short-circuit limitations are described, the conclusion reached being that reduction of ampere-turns is the only real means of increasing the short-circuit capacity.(ii).Accurate transformers for metering.—The conclusions reached are that high accuracy can and should be obtained without recourse to a large number of ampereturns, and that single-turn or bar-primary transformers with compensating windings should be used on all heavy-duty circuits.(iii).The design and application of current transformers for Protective-gear systems.— The conclusions reached are that current transformers are not necessarily the limiting features in the performance of protective gear; but that transformers for protective systems can and should be designed to be “ideal transformers” as far as the requirements of the protective systems are concerned.Voltage Transformers.—(i) General features are described, the conclusions being that voltage transformers on low voltage circuits are a satisfactory proposition subject to suitable provision of protective fuses and resistors.(ii) On high-voltage circuits means of eliminating voltage transformers are described, by utilizing an existing power transformer, and connecting the voltage transformer to the low-votltage side and compensating for regulation of the power transformer.Special-purpose Instrument Transformers.— Design and application of current and voltage transformers with varying ratio characteristics are described, especially in regard to voltage or current-change amplifiers for the more sensitive operation of relays, voltage regulators, etc.

DOI:10.1049/jiee-1.1930.0074

出版商:IEE    

年代:1930

数据来源: IET

摘要:

The phenomena of polarization and endosmose which accompany the flow of direct current in soil were investigated in various laboratory experiments. Polarization was an effect of gas bubbles on the measured soil resistance—bubbles which formed owing to a small electrolytic decomposition of the soil moisture by the current and which accumulated at the electrodes. Endosmose was extensive and occurred even against an appreciable hydraulic back-pressure. The earthing resistances of electrodes of inextensive area depend directly on the resistivity of the surrounding soil, and so relations were obtained showing the effect of moisture, temperature and salt on soil resistivity. The resistivities of coal, coke, ashes, chalk and dried soil were also obtained.Various types of electrodes of inextensive area, viz. pipes, plates and strips, were installed in aplot of ground and tested over a period covering one year. The results are important as being typical of what may be obtained in practice, but not as criteria of comparative utility of the various electrode types on account of the soil resistivity being—there were reasons to presume— appreciably non-uniform. The earthing resistances of the various electrode types were, however, calculated theoretically, a soil of uniform resistivity being assumed, and the results obtained may be used as criteria. The seasonal variations in resistance were determined during the year, and the effect of moisture in this respect was greater than that of temperature.Some electrodes of extensive area, viz. water pipes, the lead sheath of a large size cable and the steel structures of buildings, that were in the vicinity of the other electrodes, were also tested. Their earthing resistances were much smaller than those of the other types, and the smallest resistance was that of a water pipe. The possible differences between alternating-current and direct-current measurements made on electrodes in the field were investigated. The greatest difference obtained was an increase in resistance of about 20 per cent with direct current and with the positive electrode one of inextensive area.The various types of electrodes of inextensive area are considered theoretically in an Appendix.

DOI:10.1049/jiee-1.1930.0078

出版商:IEE    

年代:1930

数据来源: IET

摘要:

A description is given of a method of measuring audio frequency potential vectors with the aid of thermionic valves. The arrangement used is a modification of one originally given by A. Pages, and is adapted for tests on circuits such as artificial lines. A method of estimating the admittance existing between the input potential terminals is described.

DOI:10.1049/jiee-1.1930.0080

出版商:IEE    

年代:1930

数据来源: IET

摘要:

The application of the search-coil method of measuringHto the testing of bent magnets by the use of jointed coils is fully described. The effects of distribution of magnetizing coils, location of search coils, reluctance of the joint between magnet and armature, and radial variation of magnetizing force are examined and the conditions for the maximum accuracy of measurement are determined.

DOI:10.1049/jiee-1.1930.0081

出版商:IEE    

年代:1930

数据来源: IET

DOI:10.1049/jiee-1.1930.0089

出版商:IEE    

年代:1930

数据来源: IET