摘要:

This paper is an introduction to the Electrical Research Association's researches on arc rupture which have been in progress since 1922.An introductory section describes the genesis and aims of the research. The problem of circuit breaking is far more complicated than has been generally supposed, and can be solved only by separate study of the numerous variables involved. The apparatus, controls, and general lay-out of the testing station at Carville are described.The investigators aimed at means for preventing the arc from re-striking, rather than attacking the arc when heavy current is flowing, which may cause heavy energy release.It is shown that, in oil switches, the arc is often broken while the contacts are still within the gas bubble, so that, in such cases, arc extinction is not due to the quenching effect of the oil. Experiments have proceeded along two lines: (1) Study of the gas formed and of its arc-rupturing properties as compared with other gases, with a view to its utilization to full advantage in arc rupture; and (2) a study of the best methods of utilizing the good features of oil for like purpose, the general aim being the utilization of each method separately or in combination in improved or new types of design.Novel methods of gas-sampling during arcing are described, and the results are given of gas collection and analysis covering a wide range of currents and powers.The present paper deals mainly with arcing in gas. For given gaseous conditions in the gap between the contacts at current pause, the adequacy of the gap depends on the instantaneous value of the voltage gradient appearing across it at current zero, and it is found that, for arcs in hydrogen, the. length of critical gap is approximately proportional to the sine of the angular displacement between current and “virtual” voltage zeros. This differs radically from Bauer's conclusions. In arcs in oil there are superimposed phenomena, but in general the same law applies.With asymmetrical currents in gas and oil there is a phase-displacement effect which affects the available voltage in addition to the phase angle due to circuit conditions.Experimental results on arc-voltage characteristics are given which indicate that Norberg's application of Steinmetz's formula, if used over the range considered in the present paper, would lead to large errors in the results obtained for arc energy, whereas his experimental results, though few in number, are consistent with the results here described.A formula for arc energy when arcing takes place in gas is developed, based on simplified assumptions arising from experiment and theory. This formula illustrates the great complexity, more especially of certain known features of the time and frequency factors, which may in certain circumstances play a highly important part in affecting arc length and energy production; these appear to have been omitted in the previously published formulæ of Bauer and others.The above work leads to certain practical applications.Certain effects of arc lengthening by mechanical and electromagnetic means are discussed. This section concludes with some description of the principles of operation of a new device for arc rupturing by gas blast, which has been developed as a direct outcome of the investigation of arcing in gas. Models tested show great improvement on recognized methods of arc rupture in oil, and show promise of a satisfactory solution of the problem of arc rupture in gas, which is the main subject of this introductory paper.In spite of the added experimental difficulties due to the presence of oil in oil circuit-breakers, great advance has been made and further details will be given when the patent situation permits.

DOI:10.1049/jiee-1.1929.0048

出版商:IEE    

年代:1929

数据来源: IET

摘要:

The object of this paper is to give a description of the methods employed by the British Post Office in making telephone development studies, framing lay-out schemes and determining the economic period for which to provide plant. As the paper is to be read in conjunction with another paper * dealing with the methods employed in power systems, detailed descriptions which would only be of interest to telephone engineers have been avoided. It has thus been possible to cover a great deal of ground; but certain matters, each of which would require much space if it were dealt with adequately, have had to be dealt with in a few paragraphs. Nevertheless, it is thought that, with the information contained herein, a fair idea can be obtained of the methods adopted in the Post Office in making the studies described in the title of this paper

DOI:10.1049/jiee-1.1929.0054

出版商:IEE    

年代:1929

数据来源: IET

摘要:

The author points out that the problem of dealing with growth in the electric supply business is radically different in nature from that of the telephone business and gives an instance to illustrate the nature of the difference.To make a fair comparison with a telephone system covering a considerable area, he assumes that for comparative purposes one might deal with an area having a radius of 10 or 15 miles from the generating centre and that an alternating current system of distribution is adopted.The problem divides itself into three main heads: (1) Distribution; (2) Feeder system, and (3) Generating plant.(1) The distribution system is, of course, the root of the whole matter and it is impossible to formulate any general rules or system, especially when there is a considerable development in new buildings. The matter becomes still more difficult when factories spring up in unlikely places.Reference is made to some rough figures indicating the load which may be expected under certain circumstances, the size of distributors which might be employed, and to a flexible system which enables additional load to be handled.(2) It is pointed out that the feeder capacity must be considerably in advance of the existing distribution load, as it is not a paying proposition to put in very small extra- high-pressure feeders. Considerations of duplicate feed and economy in copper covering a given area indicate a pioneer single-line system, forming eventually part of a ring or interconnected network.(3) The problem of dealing with the situation in the generating station is one which, in future, will be very largely out of the hands of supply undertakers, and the best method is undoubtedly to plot a curve indicating the maximum load experienced from year to year. From such a curve future tendencies may be closely approximated, and the problem then resolves itself into a convenient size of unit.It is pointed out that the most economical arrangement is generally to have units of the same size; this reduces the proportion of spare plant and has certain advantages in connection with lay-out and so forth. This matter, however, is too large to be gone into at this time and is dealt with only in a general way

DOI:10.1049/jiee-1.1929.0055

出版商:IEE    

年代:1929

数据来源: IET

摘要:

An attempt is made to simplify the theory of the magnetic field round a plane circular current filament. The lines of force round such a filament are identical with the lines of flow round a circular vortex in hydrodynamics. A diagram showing these curves was drawn by Donald Macfarlane under Kelvin's direction in 1869 and has often been reproduced since. The author shows how the curves can be drawn by means of simple bipolar formulae. He shows that the mutual inductanceMbetween two concentric and coplanar circles the radii of which are a and b is given very approximately by the formulaM = 8Π2b2/a + 3√(a2-b2)Ifb/ais less than 0.5 the maximum inaccuracy of this formula is less than 1 in 40 000. Ifb/ais less than 0.7 its inaccuracy is less than 4 in 1 000. It is less than 1 per cent whenb/a= 0.9. Even whenb/ais 0.95 the inaccuracy is less than 2 per cent. A formula is given for the attraction between two coaxial circular filaments. An equation is also given from which the distance between them when their attraction is a maximum can be computed. If 6 is not greater than about the tenth part ofa, the distanceybetween them, when their attraction is a maximum, is given very approximately by2y = a + b.In a mathematical Appendix a fairly complete list is given of formulae for the two fundamental elliptic integrals and of formulae for differentiating them. Some of these formulae are new and some can only be found in treatises which are out of print and are obtainable in very few libraries. They can be usefully applied in electrical theory

DOI:10.1049/jiee-1.1929.0062

出版商:IEE    

年代:1929

数据来源: IET

摘要:

This paper deals with the ground covered by the electrical rather than the mechanical side of lift engineering. The evolution of the lift is outlined, and a description is given of the most suitable types of installations for various conditions of service.The component parts are discussed in some detail, especially the electric drive and control, and the conclusion is drawn that the Board of Trade will exercise more control in the future, particularly with regard to the mechanical design of safety devices.The use of squirrel-cage motors is considered, and it is shown that there is a big future for the " double-deck " type, which has a speed-torque characteristic similar to that of a slip-ring machine. Floor-levelling devices, too, are coming more into use as a result of the higher cage speeds now prevalent.

DOI:10.1049/jiee-1.1929.0067

出版商:IEE    

年代:1929

数据来源: IET

摘要:

The duty of the control gear is discussed. All-electric and electro-pneumatic systems, using both individual and grouped arrangements of contactors, are briefly described. The methods used for obtaining regenerative control by separate excitation of the traction motors are outlined.

DOI:10.1049/jiee-1.1929.0068

出版商:IEE    

年代:1929

数据来源: IET

摘要:

The paper outlines the trend of development in carrier telephone systems in the past, the practical application of these systems, and the working of carrier terminal, repeater and associated equipments, and then summarizes the uses and advantages of these systems.

DOI:10.1049/jiee-1.1929.0069

出版商:IEE    

年代:1929

数据来源: IET

摘要:

An aggregate consisting of an induction motor and a Scherbius series advancer will operate with a good, and nearly constant, power factor from about half full load to its maximum overload. As the load decreases, however, the advancing e.m.f. also decreases, so that on light loads the power-factor improvement is slight.In the Scherbius shunt-wound advancer the exciting winding is shunted across the rotor of the induction motor. The advancer field, and therefore the advancing e.m.f., is proportional to the current in this winding. Within the working range of slip frequencies this current, and therefore the advancing e.m.f., is nearly constant.Further, the relationship between the e.m.f.'s is such that if the advancer and slip e.m.f.'s are at right angles for any particular value of slip, they will remain so for all slips. Consequently the motor operates with a constant power factor and with its normal slip at all loads.

DOI:10.1049/jiee-1.1929.0070

出版商:IEE    

年代:1929

数据来源: IET