摘要:

Stored-program-controlled exchanges which, because of their flexibility, are generally preferred for new systems, have economic difficulties of application in practice. In a general review of the problems involved, the design of electronic exchanges is analysed, and the flexibility of the various kinds of control is assessed. It is shown that flexibility of call establishment is flexibility not of processing but of information storage, which is realisable in all systems. In respect of changes of supervision during the lifetime of an exchange, stored-program-controlled systems have an advantage over other systems which has to be assessed as cost saving during the lifetime of the exchange against cost at the initial installation. On this basis, it seems that the amount by which the capital cost of stored-program-controlled exchanges could exceed that of others is small. A system of exchanges designed for wired-logic control and for information storage which is controllable from a distance, and in which, depending on the application, wired logic is replaced by stored program to an extent determined by economy, may be the best way of relising in one system the advantages of both forms of control. A system on this basis is described in companion papers.

DOI:10.1049/piee.1971.0193

出版商:IEE    

年代:1971

数据来源: IET

摘要:

Continuing from another paper, the equipment for the structure of an electronic telephone exchange is described together with the reasons for the choices made. Analogue circuits are switched by p.a.m./t.d.m. (pulse-amplitude-modulation/time-division-multiplex) switches and p.c.m. (pulse-code-modulation) circuits by t.d.m. switches of the same kind. The use of t.d.m. switches profoundly influences the choice of processors for supervisory, signalling and other low-level functions, which, in turn, have some effect on the high-level common and unique common processors which are the subject of Pt. 2 of the paper.

DOI:10.1049/piee.1971.0194

出版商:IEE    

年代:1971

数据来源: IET

摘要:

The structure and low-level control equipment of an electronic telephone-exchange system are described in Pt. 1 of the paper. Pt. 2 expands the control to the higher levels of register and unique common control and describes the operation of the whole system. The main problem and objective of the control system is to be economical for all sizes of exchange, for which purpose its cost must be approximately proportional to the size of exchange with only a small constant cost independent of size. To this end, advantage is taken of the low cost, concomitant with the use of t.d.m. (time-division multiplex) switches, of guide-wire path selection and distributed processors to reduce the cost of the unique common processor, the cost of which is minimised by a combination of wired and stored-program logic, the stored-program-logic part being remotely located and shared with other exchanges if an exchange is too small to support it alone.

DOI:10.1049/piee.1971.0195

出版商:IEE    

年代:1971

数据来源: IET

摘要:

A variational principle based on duality is developed which is related to the complementary variational principle recently established. As a result, classes of solutions other than those normally obtained can be found for the characteristic impedance of TEM lines. In principle, two separate upper and two separate lower bounds can be determined. A simple example, for which the exact solution is known, is used to illustrate the methods.

DOI:10.1049/piee.1971.0196

出版商:IEE    

年代:1971

数据来源: IET

摘要:

The results of a noniterative simplified load flow are used as starting values for the Newton-Raphson algorithm. This scheme improves the reliability of the Newton-Raphson method, to the extent that convergence for any physically feasible problem is envisaged, and gives high-accuracy solutions in two or three iterations. The starting process has a number of other valuable uses and may be employed on its own to give fast approximate a.c. load flows.

DOI:10.1049/piee.1971.0197

出版商:IEE    

年代:1971

数据来源: IET

摘要:

Some transients in linear a.c. circuits can be advantageously described by a slowly varying phasor. This is true also for a quasilinearRLCnetwork, linearised at the point of near-resonance operation, for a small-perturbation stability analysis. The linearisation of a nonanalytical complex function indicates a tensorial relationship between the variables, but this is not uncommon in other well known electric-circuit applications such as synchronous machines and current transformers. The stability analysis is performed by calculating, step by step, the trajectory of a small initial perturbance phasor. It is illustrated by the example of a seriesRLCcircuit and a capacitive voltage divider with a quasilinear inductive load.

DOI:10.1049/piee.1971.0198

出版商:IEE    

年代:1971

数据来源: IET

摘要:

A general form of computation logic is established for single-phase and 3-phase circuits containing one or more thyristors. Two examples studied in detail are the single-phaseRLCcircuit with one thyristor and the 3-phase, fullwave, 6-thyristor bridge circuit with anRLCload. Good agreement was found between computed and experimental results.

DOI:10.1049/piee.1971.0199

出版商:IEE    

年代:1971

数据来源: IET

摘要:

An account is given of the development of overhead equipment for use on British Railways electrification schemes during the period 1960–1970. These developments have led to equipment having improved dynamic performance and lower cost. Concurrently, the efficiency of installation has been increased. Economies have followed the disappearance of steam locomotives, allowing the use of less expensive materials for metal fittings and insulators. Other improvements have arisen from steady development and the application of new techniques. Dynamic performance has been improved by the use of sagged simple-catenary equipment, damping of the pantographs and optimisation of span profiles, dropper spacings etc. Cadmium-copper conductors have in nearly all cases, been replaced by hard-drawn copper or by steel-reinforced aluminium. Supporting structures have been simplified, and sometimes replaced by headspans, and tensioning and anchoring arrangements have been improved. Resin-bonded glass-fibre arms combining the functions of spring support and insulator have been used to improve tunnel equipment, and many other improved insulators using glass fibre and other materials have been developed. By careful attention to detail, the multiplicity of individual components has been reduced to a much smaller number of interchangeable components. Bonding techniques have been improved, and bonding has been simplified. Economics have been achieved by detailed planning and co-ordination of constuction and operating activities.

DOI:10.1049/piee.1971.0200

出版商:IEE    

年代:1971

数据来源: IET

摘要:

This paper illustrates by example how a method of optimisation used in the electrical-engineering field is extended and applied to that of gas engineering. This approach of optimising a general gas system is formlated as a general nonlinear programming problem. All the system parameters are expressed in mathematical representation. The usage of natural gas is also included. An iterative approach based on the Lagrangian-multipliers method with penalty functions for the inequality constraints is presented as the method of solution. A small sample system which consists of the essential parameters of a gas system is solved. A compact storage scheme is employed which makes the method commercially attractive.

DOI:10.1049/piee.1971.0202

出版商:IEE    

年代:1971

数据来源: IET

摘要:

The author presents an analytical solution of Maxwell's equations for the fields in a finite-length, solid-rotor induction motor in which the rotor is not fitted with conducting endrings. It has been assumed as a boundary condition that zero flux enters the ends of the rotor; this is borne out by tests on a typical machine. The solutions for the field distributions are approximate only, but the approximations are good over a wide range of slip. A major advantage of the solutions is that they are expressed in closed, rather than series, form. It is shown that the field distributions and the equivalent-circuit impedances may be considerably different from those obtained by ignoring finite-length effects. Some simple criteria are derived to assess the importance of finite-length effects on machine impedances. The analysis is carried out ignoring rotor saturation and slotting.

DOI:10.1049/piee.1971.0204

出版商:IEE    

年代:1971

数据来源: IET