摘要:

The subject of this paper is the jet-wave rectifier, a purely mechanical device which, in the course of the last 15 years, has been developed into a means for high-power rectification. Prototypes of the constituent parts of the apparatus have been described elsewhere; in the present paper it is shown how the rectifier can be designed on the basis of these prototypes, and especially on the result of investigations with regard to the theoretical relations between their qualities. These relations are stated and are used in working out examples of typical designs. In addition, a review of the general properties of the jet-wave rectifier, and anticipations with regard to its future development, are given. It is concluded that a new high-capacity rectifier, of a character quite distinct from that of the mercury-arc rectifier, but likely to be used for similar duties, has been brought into existence.

DOI:10.1049/jiee-1.1930.0105

出版商:IEE    

年代:1930

数据来源: IET

摘要:

The following investigation is concerned with the operation of a rotary convertor during conditions of abnormal loading, such as violent fluctuations occurring at definite intervals or during short-circuit conditions. In the former case the rotary convertor, being an oscillatory system having a natural period of its own, behaves just like any mechanical oscillatory system which is subjected to uniformly timed impulses. It is shown that when the natural and the forcing periods synchronize, resonance takes place and very large displacements may be set up, not only with the fundamental period of the disturbance but also by selective resonance with any harmonics which may be present. Methods of determining the natural period of the convertor and of calculating the amplitude of the oscillations set up under specified conditions are given, the methods being verified by experimental results.The second part of the investigation deals with the motion of the rotor when the machine is subjected to a short-circuit of short duration. The mechanical analogy is in this case a ballistic pendulum, and expressions are developed which enable the displacement and slip velocity to be determined at the moment the short-circuit is cleared, and also the motion subsequent to clearing. These expressions also are verified by experiment, and considerable light is thrown on the requirements of the quick-acting circuit breakers which are commonly used on the d.c. side of rotary convertors.The research has, of necessity, been conducted on a small experimental machine, but the theoretical and experimental investigations are found to be in reasonably close agreeement and, in the case of the operation under short-circuit conditions particularly, it is possible that some other investigator having the necessary facilities may be induced to repeat the investigation on a machine of commercial size.

DOI:10.1049/jiee-1.1930.0109

出版商:IEE    

年代:1930

数据来源: IET

摘要:

It is shown that when planning a lighting system for a large “ working plane” using the standardized industrial reflector (B.S.S. No. 232—1926), it is better to place the lamps over the centres of certain contiguous rhombuses than over the centres of contiguous squares of equal area. A new definition is proposed for the term “spacing ratio.” A convenient method of drawing isolux diagrams is described and such diagrams are given for the above-mentioned standardized reflector at a spacing ratio of 1.5. It is shown how uniformity of illumination varies with spacing ratio with the above reflector. A plea is made that manufacturers of other reflectors should publish similar information relating to their goods. Finally, some brief practical rules for designers of electrical lighting systems are given, from whose point of view the paper has been written.B.Sc.(Eng.)

DOI:10.1049/jiee-1.1930.0110

出版商:IEE    

年代:1930

数据来源: IET

摘要:

The method of testing straight samples of high-permeability material, by using search-coils for the measurement ofHand eliminating flux leakage from the length under test by means of compensating magnetizing windings, has been previously described in relation to permeability measurements. Its application to hysteresis measurements is found to involve more complicated switching operations, but a comparison of results obtained on bars and strips with those for rings of similar material shows good agreement when compensation is employed at each point on the loop. In the absence of compensation, large differences occur between the loops determined for straight and ring specimens.In tests on magnet-steel bars compensation produces a negligible effect on the results and is unnecessary.A drum controller to perform the switching operations required in carrying out a hysteresis loop under compensated conditions is described.

DOI:10.1049/jiee-1.1930.0111

出版商:IEE    

年代:1930

数据来源: IET

摘要:

The paper contains an account of experiments carried out by the authors to analyse some of the various factors concerned in the behaviour of induction watt-hour meters, with particular reference to the changes in accuracy produced by different frequencies.The subject is dealt with under the following headings:—Experimental determination of the changes in accuracy of induction watt-hour meters with changes in frequency.The causes of the changes, namely braking effect of the voltage flux, and reactance of the disc.Separation of the two effects, and determination of their relative magnitudes.Determination of the time-constants of the discs.Explanation of the torques produced in induction meters.Determination of some of the other phase errors in the meters.Conclusions.

DOI:10.1049/jiee-1.1930.0112

出版商:IEE    

年代:1930

数据来源: IET

摘要:

In this paper the various ways are considered in which a 3-electrode valve should be used in a thermionic voltmeter, and the accumulated experience is described of several years' work by the author in making valve voltmeters for various purposes. No one arrangement can possess every desirable property, and it is shown how to produce a voltmeter to fulfil specified requirements. The effective input resistance of the various arrangements, and the harmonic currents produced by grid current, are the harmonic currents produced by grid current, are considered analytically and experimentally. The effect on range and sensitivity of providing additional batteries is also discussed, extra batteries being found to be an advantage only in very low-range instruments.The effect on the calibration of a change in the valve and in temperature is found to depend on the form of the rectifier used. In general, a thermionic voltmeter cannot read R.M.S. values. The wave-form error of various systems is investigated; with one arrangement the reading is proportional to the peak voltage and in another to the mean. The possibility of a frequency error is discussed; tests show that the error is negligible for frequencies up to 1 000 kilocycles per sec., whilst from indirect tests it would appear that the error is probably negligible for frequencies up to 30 times this value.

DOI:10.1049/jiee-1.1930.0114

出版商:IEE    

年代:1930

数据来源: IET

摘要:

Part(1) describes a four-aerial direction-finding system erected at a site near the Radio Research Station, Slough, and gives details of the tests carried out on this apparatus at wavelengths of 300 to 600 m. The system is based on the Adcock principle, but a modification has been introduced to correct for the asymmetry of the aerial system with respect to its upper and lower portions which is unavoidable if the operating hut is at ground-level.In the first test the performance of the new direction-finding system was compared with that of a rotating-loop direction-finder over a prolonged period which included conditions of most severe “night effect.” In the second test a calibration of the system was made by means of a transmitter attached to a kite which provided a source of downcoming waves of known angle of incidence and polarization.The results of the tests show the new system to be considerably superior to the closed-loop system for conditions of “night effect.” They indicate, however, a residual instrumental error of the system in the presence of down-coming waves. Finally, a further modification of the system by which it is hoped this will be eliminated is described.Part(2) describes two distinct types of portable short-wave direction-finding apparatus and gives details of the methods by which they were tested and compared under working conditions at wavelengths of 12 to 60 m.The first instrument is of the totally-screened closed-loop type.The second instrument is of the rotating Adcock type consisting of a single pair of spaced vertical aerials pivoted about a vertical axis.The tests described are divided into four sections:—(a) Testa for instrumental error with a local transmitter situated first on the ground and then elevated 40 ft. above the ground with its aerial at various angles to the vertical to give waves of varying polarization.(b) Tests on the effects of the immediate surroundings of the receiver.(c) Direction-finding observations on the “ground ray” of a transmitter up to the maximum distance at which the ray is detectable.(d) Long-range tests at which only downcoming waves were being received.Test (a) showed the Adcock to be much superior to the loop in the presence of downcoming horizontally polarized waves, while, (b), (c) and (d) show that for observations on the ground ray both instruments are equally satisfactory and that with due precaution in the choice of a site their performance is much the same as that the of longer-wave apparatus. For observations just outside the range of the ground ray both systems are equally useless, while at greater ranges (beyond the “skip distance”) the results again demonstrate the superiority of the Adcock to the loop.It is shown that the results generally confirm the conclusions with respect to the nature of the propagation of the waves arrived at by Eckersley from somewhat similar experiments.

DOI:10.1049/jiee-1.1930.0115

出版商:IEE    

年代:1930

数据来源: IET