DOI:10.1049/ji-2.1946.0001

出版商:IEE    

年代:1946

数据来源: IET

摘要:

The paper records the development of the generation of d.c. power in aircraft by windmill- and engine-driven generators, from its inception to the present day. The developments prior to the last decade are covered only very briefly.Features of generator design which have called for special consideration, or have been the subject of failure, are discussed. Sections are devoted to the choice of speed range, brush wear at high altitude, systems of ventilation, design of end-frames, and bearing failure. Some mention is made of generators designed for power supply to radio equipment, as distinct from general power services. These generators, which include high-voltage d.c. machines and high-frequency a.c. machines, have been combined with low-voltage d.c. machines, both in tandem and with a common magnet system.The latter part of the paper deals with voltage regulation, which is inseparable from the preceding part, in so far as generator design is influenced by the system adopted; self-regulating generators of various types have been used from time to time in the past. The scope does not permit more than brief mention of the design of the several types of regulator which have been used, including Tirrill and carbon-pile types.The paper shows how the control of the system voltage has been conditioned by the inclusion of an accumulator, and how it has not been possible to devise a system which gives the constant line voltage required for current-using devices, and, at the same time, permits of adequate control of accumulator charging current. Systems of paralleling, and their effect on line voltage, are also described.The electrical equipment of lighter-than-air craft is not included in this paper.

DOI:10.1049/ji-2.1946.0002

出版商:IEE    

年代:1946

数据来源: IET

摘要:

With a view to obtaining a more fundamental knowledge of the phenomena relating to meter and instrument bearings and to improving such bearings, research has been carried out for a number of years on behalf of the Electrical Research Association at the Meter Testing Laboratories of The Northmet Power Company. This paper gives a brief survey of the various aspects covered by this research, dealing mainly with the sapphire/steel combination, both dry and lubricated, but also includes other combinations of materials.The apparatus and methods of test are outlined, followed by a survey of the results from life tests, including an analysis of the various factors which contribute to wear. The results of a microscopical examination of the units at the end of their life run are discussed. A brief theory of the boundary lubrication existing in such bearings is given, with a short extract of the detailed discussion of the various factors disclosed in E.R.A. Reports T/T31 and T/T39.Mathematical formulae developed during the research have been simplified into nomograms.The results of experiments on the resistance of sapphire jewels to impact forces are given. The phenomena associated with bottom bearings at various loads, caused by parasitic forces existing in meters, are also dealt with.The actions of the ball-type bearing and that of the pivot bearing are compared, and an approximate estimation of the life of bearings in practice, based on life tests, is made.

DOI:10.1049/ji-2.1946.0003

出版商:IEE    

年代:1946

数据来源: IET

摘要:

Of the two main groups of electrical machines, those with alternating, mostly rotating, and those with pulsating, mostly swinging, fields, the second has advanced more rapidly in recent years. A variety of new inductor-type machines have been developed for telecommunication and industrial purposes. The paper suggests that, instead of attempting to adapt the rotating-field theory to pulsating-field machines, it is more satisfactory to employ an independent theory developed by finding an expression for the pulsating permeance of the magnetic path and considering the total m.m.f. acting upon that permeance, both on open-circuit and on load. A new method for determining rapidly the air-path permeance as a function of time leads to the “belt characteristics,” thence to the e.m.f. and its waveform on open-circuit, to the armature reaction including its effect on the waveform, and to the necessary excitation for a given load. The analytical results are supplemented by simple vector diagrams. The means for controlling the waveform are then discussed, among them a new device for eliminating undesirable odd harmonics in addition to the even harmonics. Finally, suggestions are made for simplifying the work in design offices by standardizing the most favourable slotting and the corresponding characteristics.

DOI:10.1049/ji-2.1946.0006

出版商:IEE    

年代:1946

数据来源: IET

DOI:10.1049/ji-2.1946.0015

出版商:IEE    

年代:1946

数据来源: IET

摘要:

This paper reviews the various types of alternators available for the generation of frequencies up to 50 000 c/s, and shows that for the majority of applications the modern heteropolar inductor alternator is the most suitable machine. It demonstrates that this alternator is superior to the older homopolar and heteropolar types, owing, in the case of machines required for frequencies of 400 to 3 600 c/s, to a system of field and armature windings which substantially reduces the number of armature conductors required to generate a given e.m.f. For frequencies above 3 600 c/s this superiority is due to a combination of these windings with a stator slotting arrangement which permits, for a given frequency and speed of rotation, a large reduction in the number of wound stator slots. The electrical characteristics and mechanical construction of these alternators are discussed, together with their application to the melting of metals and surface-hardening of steel. An appendix gives a brief mathematical treatment of the theory of their novel features.

DOI:10.1049/ji-2.1946.0016

出版商:IEE    

年代:1946

数据来源: IET