摘要:

The object of this paper is an attempt to point out the advantages of combining the production of electrical energy with that of coal by-products. It is also a plea for co-operation between the mine owners and electrical engineers, especially in districts where there already exist efficient gas-engine stations utilizing waste gas, and in other districts where they can be efficiently erected and operated.It is an admitted fact that the Electricity Act of 1926 will have a very far-reaching influence not only throughout the electrical industry but also in the homes and lives of the people, and if therefore the thermal and financial aspects of that Act are carefully considered it should lead not only to cheaper electricity but also to a greater use of the coalfields as generating centres.It has been said in the past that the general view of the generation of electricity is too parochial, and that if the country as a whole is to benefit from the proposed re-organization of the generation of electricity the widest possible outlook should be taken. This outlook must embrace the generation of electricity and also the possibility of reducing unemployment by encouraging the mining industry to cooperate, not only in the supply of fuels but also in that of surplus electrical energy.

DOI:10.1049/jiee-1.1928.0105

出版商:IEE    

年代:1928

数据来源: IET

摘要:

There are at present two distinct methods of rating in use in Great Britain for ordinary-duty fusible cut-outs. The first method is that given in B.S.S. No. 88 and is based on an absolute value of minimum blowing current difficult to determine. The second method, that specified in the I.E.E. Wiring Regulations, adopts the “1-minute blowing current” as a basis. The former method is generally admitted to be unsatisfactory from a practical standpoint, and the latter method is shown herein to be unsuitable for semi-enclosed cut-outs employing tinned copper fuse-links.The present report reviews British, Continental and American practice, deduces a method of rating suitable for existing British designs, and provides the experimental data required for a revised specification.The problems confronting a designer in calibrating a range of cut-outs to comply with the revised basis are dealt with in detail, together with the simple tests by which the user may check the rating in practice.The information contained herein will be of service in connection with the revision of B.S.S. No. 88 which is now being carried out; but in the interim before a new specification is issued it is thought that a useful purpose will be served by subjecting the proposals to the criticism of designers and users.

DOI:10.1049/jiee-1.1928.0107

出版商:IEE    

年代:1928

数据来源: IET

摘要:

In most problems on antenna systems the field at any point is assumed to be one or other of the so-called induction and radiation fields. Actually it is a combination of the two and in some cases the “static” electric field has to be considered. All antenna systems are designed to give a specific radiation field in certain directions. It would simplify problems connected with antenna systems and, in particular, beam systems, if the total field at any point in space were expressed in the form of a radiation field. In order to take account of the apparent change in type of field as we recede from the antennæ, the equation for such a field must contain two variable factors depending on the distance. One of these governs the phase and the other the amplitude of the total field. In this paper these factors are calculated and curves are plotted giving their values for different distances. The best position for a reflector is then considered and it is found not necessarily to be at a ¼ wave-length behind the transmitter, as is commonly supposed.The method of calculating from the curves the required positions of antennæ in a system for any given purpose is shown. Two specific cases are considered. One corresponds to the parabolic reflector and the other to the linear curtain system. It is shown that the envelope of the reflecting antennæ when these are tuned is not quite a parabola. In a beam system with a linear antenna array, it is found that good conditions are obtainable if the transmitting antennæ are spaced 0.72 wave-length apart and the reflector is in line ¼ wave-length behind, with the individual antennæ midway between the two corresponding antennæ of the transmitter.The experimental results of Tatarinoff appear to confirm the theoretical results obtained.

DOI:10.1049/jiee-1.1928.0109

出版商:IEE    

年代:1928

数据来源: IET

摘要:

After introducing the terms “directive efficiency” and “sharpness of directivity,” the author considers the general conditions for obtaining good sharpness of directivity in a beam system.Supposing that the field strength is required to vary rapidly for angular displacements in a certain plane in the neighbourhood of a certain direction, it is found that the antenna system should be spread in the plane under consideration and in a line perpendicular to the direction of maximum radiation. When a plane reflector is used the system should lie in aline which is not quite perpendicular to the direction required, in order to obtain optimum results.If the antenna system is to hold within a fixed volume, one side of the volume should be as large as possible. At the same time a certain relation should hold between the lengths of the sides and the direction in which radiation is required.It will be evident that, since in a parabola the antennæ do not lie in a straight line, the parabolic system is not, for given overall dimensions, the best arrangement for obtaining good sharpness of directivity.A good reflector should be at a definite distance from the transmitter in order that the phase of the radiation fields from the reflector and transmitter respectively may be zero in one direction and 180° in the other. Even when this obtains, the reflector will act in this way for only one direction. For instance, a reflector adjusted to neutralize the radiation in a certain direction in the horizontal plane will not do so in any other direction or in any other plane.A method using an inclined antenna system and reflector for the purpose of obtaining maximum sharpness of directivity at any angle to the vertical is described.Finally, the question of excitation is very briefly considered, and it is suggested that antennæ not directly connected to the source may be used. A possible improvement on the Franklin antenna is also described.

DOI:10.1049/jiee-1.1928.0110

出版商:IEE    

年代:1928

数据来源: IET

摘要:

The problem dealt with is the calculation of the effective e.m.f. induced in a receiving antenna from the field of a neighbouring transmitting antenna. It is assumed that the distribution of the current in the transmitting antenna is known. In this connection the author has shown that, for the simple antennæ usually met with in practice, the current distribution can be readily calculated.The various parts of the problem are taken separately. First, the formulæ for the field at a point due to any element of current are given, and it is shown that the wave-form of the field varies with the distance from the antenna.The next point deals with the polar diagram at large distances of an antenna. With regard to the wave-form, it is pointed out that the usual spectrum of the current of a radio station consists of a number of peaks at frequencies which are whole multiples of the first, each peak having a fairly rapidly decreasing intensity for a comparatively small range of frequency on each side. The peaks correspond to the fundamental and the harmonics, and on each side are the side bands of the modulation. It is pointed out that the polar diagram of the harmonics may differ very considerably from each other, but that, for the frequencies of the side bands, the directions of the maxima of radiation would not be appreciably different from the directions of the maxima of the corresponding harmonic.The effect of the conductivity and dielectric constant of the earth is next considered, the image due to any given element of current being taken as the exact image of the current element, but havingKtimes the intensity. The factorKdepends on the angle of incidence at the earth, the nature of the polarization of the incident field, the electric constants of the earth, and the frequency. This, again, will therefore produce an effect on the wave-form of a received signal.Finally, a formula is given for the effective e.m.f. induced in a simple receiving antenna when the field at any point along the antenna is known. This formula applies even if the field is not uniform.In conclusion, the problem of interference is considered. It is suggested that a criterion for the interference of a radio station dependent on the current and potential spectrum at the foot of the antenna would be convenient. A new spectrum calculated from these would give the variation of the sum of the squares of the current and potential with frequency, for the harmonics and average working modulation of the station. From a rough calculation the maximum energy of radiation for a unit current at the various frequencies of the spectrum could be calculated and, possibly, combined in some suitable arbitrary way with the maximum energy of radiation along the ground. The product of this arbitrary relation and the spectrum distribution, obtained as explained, would form a convenient basis of a criterion for the measurement of interference.

DOI:10.1049/jiee-1.1928.0111

出版商:IEE    

年代:1928

数据来源: IET

摘要:

The chain of resonant circuits coupled by mutual inductance is reduced to the more usual type of filter circuit or chain of T-links in Section 1. In Section 2 a solution is obtained for the currents flowing, and this is applied to the chain of resonant circuits in Section 3, and to the case of a chain of asymmetrical T-links in Section 4. In the last Section a graphical construction of the solution is worked out. An appendix gives an example.

DOI:10.1049/jiee-1.1928.0112

出版商:IEE    

年代:1928

数据来源: IET

摘要:

The paper deals purely with the economic aspect of powerfactor correction in transmission systems; it is not intended to bear on the subjects of voltage regulation or stability, nor is it concerned with the problem of power-factor improvement in electrical machinery.In brief, the losses in a transmission line supplying power to a load having a power factor less than unity can be reduced by power-factor correction at the receiving end, the most economical system being that in which the annual saving in the transmission-line losses due to power-factor correction shows the greatest margin over the total annual cost of the plant installed to provide that correction.The author arrives at general expressions which give for any particular case, on inserting relevant practical figures for various constants and basic costs, the most economical degree of power-factor correction and hence the best rating of synchronous or other condenser equipment.

DOI:10.1049/jiee-1.1928.0113

出版商:IEE    

年代:1928

数据来源: IET

DOI:10.1049/jiee-1.1928.0114

出版商:IEE    

年代:1928

数据来源: IET

DOI:10.1049/jiee-1.1928.0116

出版商:IEE    

年代:1928

数据来源: IET

DOI:10.1049/jiee-1.1928.0117

出版商:IEE    

年代:1928

数据来源: IET