摘要:

The paper describes an experiment made by London Transport on a novel system of control of regeneration with multiple-unit stock. It lists the difficulties and explains the means by which they were overcome. Three equipments, designed by three electrical manufacturers in close co-operation with London Transport to satisfy the conditions of regeneration, are described and the various problems arising during the tests, with their solutions, are explained. Economic factors to be assessed are given.

DOI:10.1049/pi-a.1962.0118

出版商:IEE    

年代:1962

数据来源: IET

摘要:

The paper describes the progress made since 1945 in the electrification of the Southern Region of British Railways on the 750 V d.c. conductor-rail system. It gives details of fixed equipment, rolling stock and locomotives, and also touches on the important ancillary role of Diesel-electric propulsion in achieving the complete elimination of steam traction from an electrified area. There are particulars of loads on the national supply system created by extensions of electrification, and some mention is made of dual-powered locomotives, maintenance matters and future electrification policy on the Region.

DOI:10.1049/pi-a.1962.0119

出版商:IEE    

年代:1962

数据来源: IET

摘要:

The principles and advantages of transductor-assisted tap changing are described and the design of a particular a.c. locomotive incorporating this feature is explained.The particular type of transductor circuit employed is examined in detail, together with the reasons for its selection, its method of operation and its performance in practice.The advantages to locomotive performance of controlling the tap changer so as to automatically regulate the traction current are discussed and the performance of a prototype system is described.

DOI:10.1049/pi-a.1962.0120

出版商:IEE    

年代:1962

数据来源: IET

摘要:

The paper outlines the development of a new type of pole-change motor giving three or five speeds. The development is an extension of the principles of ‘phase-mixing’, which were explained in an earlier paper which described a continuously-variable-speed brushless induction motor. In the earlier machine a fraction of the periphery could not be used owing to the continuously variable pole-pitch requirement, and the stator windings in the active arc were fed from phase-shifting regulators.The present paper shows how acceptance of a finite number of specific speeds may be exploited to enable the whole of the periphery of the machine to be used, and, at the same time, to replace the phase-shifting regulators by switches. The complexity of the switch arrangement depends on the number of speeds required. The paper concludes by describing 2-speed machines based on the phase-mixing principle in which the number of terminals on the machine is reduced to six.Theoretical investigation of the harmonic effects is considered, and this material is supported by experimental results obtained from several machines. High values of copper utilization and low harmonic content are shown to be possible with the phase-mixing technique.

DOI:10.1049/pi-a.1962.0122

出版商:IEE    

年代:1962

数据来源: IET

DOI:10.1049/pi-a.1962.0124

出版商:IEE    

年代:1962

数据来源: IET

摘要:

The paper describes the development of a new type of a.c. generator in which the moving member travels between a d.c. pole structure in a straight line with reciprocating motion. Tha induced e.m.f. appears in the moving member, which consists of a single loop of conducting material which embraces and moves along the core. The core carries stationary coils which experience an induced alternating e.m.f. by transformer action from the moving loop. These coils are not associated with the air-gap between the d.c. poles and are more easily cooled than the windings of a rotary machine. The loop, which is confined to the air-gap, can be run at high temperature, since it carries no insulation. The machine can be used as a generator to convert mechanical power supplied directly from a piston. It can also be used as a synchronous motor for such purposes as the driving of compressors without cranks; when used in this manner the machine is self-starting. Essentially a single-phase machine, the equivalent of multi-polar rotary machines can be constructed which will generate e.m.f.'s at 50c/swith mechanical oscillations at frequencies lower than 3 000 per minute.The construction of the machine is simple, since the core is made up entirely from rectangular stampings, while the windings consist of four transformer-type coils and a conducting loop.An experimental machine is described, development of which consisted largely of testing devices to minimize the internal impedance Test results are given.The paper includes a proposed design for a 33 kVA generator.

DOI:10.1049/pi-a.1962.0125

出版商:IEE    

年代:1962

数据来源: IET

摘要:

The paper describes the application of an analogue computer to the study of the transient stability of a synchronous generator when subjected to an unsymmetrical fault. The system is analysed by the method of symmetrical components and reduced to a form in which it is readily represented in a direct- and quadrature-axis reference frame, which is most convenient for simulation on an analogue computer.Results are given of a specimen study on a machine connected to an infinite system. Saliency and flux decay are taken into account, and the effect on stability of the negative-sequence torque in the machine is shown. The simulation of the machine is based on the operational form of Park's equations.

DOI:10.1049/pi-a.1962.0129

出版商:IEE    

年代:1962

数据来源: IET

摘要:

For many years special difficulties have been experienced with sliding contacts, especially commutators, in aircraft generators. These difficulties have been attributable chiefly to the high running speeds, the dry rarified air at high altitudes and the wide range of temperatures encountered. Improvements in commutators and brushes have been made at considerable cost, but at a rate which, if continued, would not keep pace with contemporary advances in aircraft performances.Fortunately the silicon rectifier has now been developed to the point at which it can be used as a static commutation device. The characteristics of silicon rectifiers and their application to the commutation of polyphase alternating currents generated in rotating machines are discussed and some of the fundamental limitations are indicated.The known types of brushless generator are then described; they may be divided into three main groups. The first includes permanent-magnet and induction generators, whose inherent charateristics are unacceptable for aircraft applications.The second, and at present most important, group comprises a.c. and d.c. generators with revolving field windings which are energized through shaft-mounted (rotating) rectifiers from the armature of an a.c. exciter. These generators have been fully developed and proved in aircraft service, and can be cooled with air at an inlet temperature up to 150°C. With further development and improved rectifiers it is believed that this temperature can be raised to at least 200° C. These inlet air temperatures are normally associated with supersonic aircraft speeds and a substantial drag penalty for air cooling, and in very-high-speed aircraft of the future liquid cooling may be preferred, if not inevitable. Liquid cooling does, however, add to the complexity of a generating system. Partly for this reason much attention has been paid in recent years to generators with stationary field windings which do not require rotating rectifiers and which, it is hoped, can be cooled with air at inlet temperatures up to 250° or 300° C. The various types of generator of this kind constitute the third main group. Careful studies have shown that they are all about 40–50% heavier than equivalent generators of the rotating-rectifier type, and prototype solid-rotor generators have revealed difficulties of construction which, although not insuperable, have yet to be resolved. Nevertheless, these generators hold promise of simplicity with attendant reliability for severe operating conditions.

DOI:10.1049/pi-a.1962.0130

出版商:IEE    

年代:1962

数据来源: IET

摘要:

Steel-cored aluminium conductors in coastal districts are sometimes subjected to a severe form of electrolytic corrosion which can cause the conductor to break when there is a high load current. The effects of this corrosion are usually very local and are difficult to detect without special equipment. The paper describes a trolley-mounted gauge that can be towed along an unenergized conductor by an operator on the ground, who is warned when a bulge, which is the external manifestation of this corrosion, is traversed.With only one cord thrown over the conductor, it is possible for the operators on the ground to raise the detector to the conductor, secure it in the working position, release it and lower it to earth.

DOI:10.1049/pi-a.1962.0132

出版商:IEE    

年代:1962

数据来源: IET

摘要:

As the overload capacity of cables is governed by their temperaturerise/time characteristics a convenient and relatively rapid means of predicting these characteristics is of great utility. A resistance-capacitance type of electrical analogue simulating the thermal problem of three single-core high-voltage oil-filled cables laid direct in soil in horizontal formation is described.The temperature-rise/time characteristics resulting from step functions of cable copper loss are obtained for points in the cables and the surrounding soil, and those for the cables are shown to comprise three distinct exponential terms. The effects of dielectric and sheath losses are also investigated.A modified form of the analogue is used to simulate cooling by means of the flow of water through two tubes laid between the cables. The thermal time-constants in these conditions are seen to be much smaller than without water cooling, and a large uprating is possible. Of the total heat evolved 73% is dissipated into the water.A simplified analogue of one single cable is also described, and the transients obtained are compared with those resulting from published analytical methods.

DOI:10.1049/pi-a.1962.0133

出版商:IEE    

年代:1962

数据来源: IET