摘要:

The paper deals with a detailed investigation of noise measurement for the purpose of establishing methods generally applicable to the sustained noises encountered in engineering. The work follows on that described in a previous paper. The necessity for redetermining the properties of the hearing system of the average individual in terms of free-space conditions of listening is explained, and the results obtained on 60 persons are given. The inadequacy of the decibel scale for indicating subjective loudness is discussed and two alternatives are considered. The second of these is suggested as being the more helpful in conveying numerically the desired impression of loudness.Desirable improvements in the noise-analysing apparatus described in the previous paper are indicated, and a new equipment embodying these features is briefly described.The various methods of assessing the loudness of a complex noise are considered in relation to engineering requirements, and the reasons are given for the choice of the aural balance method using a pure reference tone with a frequency of 800 cycles per sec. Experience obtained with this method in assessing typical noises is described. Finally, consideration is given to the problem of specifying the noise which a piece of apparatus may make when installed in a particular location.

DOI:10.1049/jiee-1.1934.0146

出版商:IEE    

年代:1934

数据来源: IET

DOI:10.1049/jiee-1.1934.0155

出版商:IEE    

年代:1934

数据来源: IET

摘要:

This paper deals with various errors that may arise when a moving-coil instrument is used in conjunction with a copper-oxide rectifier to measure alternating currents and voltages.The effects of circuit impedance upon the reading of a rectifier ammeter and of the amount of series resistance upon the reading of a rectifier voltmeter are investigated. It is also shown that the effective resistance of a rectifier as calculated from tests with different series resistances varies considerably, owing to the distortion of the current wave even when the voltage is sinusoidal.The use of rectifier instruments having linear characteristics to measure very bad wave-forms, such as telephonic currents, is dealt with; and it is shown that such instruments, calibrated with a sine wave, read the effective value within about 10 per cent for any shape of wave, however much it may be distorted.Finally, the difficulties encountered in the application of rectifier instruments to current transformers are examined and methods of reducing those difficulties are suggested.

DOI:10.1049/jiee-1.1934.0156

出版商:IEE    

年代:1934

数据来源: IET

摘要:

Methods at present in use for determining form factor are outlined, and their good and bad features are indicated. A description is given of a new instrument, incorporating a copper-oxide rectifier, which gives direct indications of the form factor. Test results show that the instrument is sensibly independent of variations of voltage, frequency, and temperature. The form factors of waves of varying shape are shown to be correctly indicated, except in the cases of re-entrant waves, and rectangular waves of a particular type. The effects of this last class of waves are discussed in an Appendix.

DOI:10.1049/jiee-1.1934.0157

出版商:IEE    

年代:1934

数据来源: IET

摘要:

Rubber latex consists normally of a suspension of minute negatively charged rubber globules in an aqueous serum. Under electrolytic stress, therefore, the globules tend to migrate towards the anode.By using anodes of suitable metal, e.g. zinc, or a porous diaphragm round the anode, it is possible to effect electro-depostion of the rubber. With suitable conditions, and using compounded latex, deposits are obtainable which can be dried and vulcanized. Commercial manufacturing processes have been based on this principle.The possible modifications in the conditions of electro-deposition permit numerous and interesting variations in the details of the procedure and of the results.The use of latex in this way obviates the customary need for the heavy machinery used in ordinary rubber manufacture and eliminates the preliminary milling treatment of the raw rubber, so that the mechanical properties of the product are correspondingly improved.

DOI:10.1049/jiee-1.1934.0160

出版商:IEE    

年代:1934

数据来源: IET

摘要:

A brief survey is given of recent modifications in the construction of gas-focused cathode-ray oscillographs, and some of the resulting improvements in performance are described.The authors then summarize recent work of other investigators which has a direct bearing on the subject matter of the present paper.A comparison is made of the electrostatic sensitivities obtained from simple electron dynamics and that found by experiment for two focusing gases, argon and helium; an explanation is advanced for the results obtained.The phenomenon of origin distortion is next considered, and results are given showing its variation with gas pressure for hydrogen, and with the frequency of the deflecting voltage between 0 and 1.25 ×104cycles per sec. for hydrogen, helium, and argon, as focusing gases.The dependence of gas focusing on the transverse speed of the electron beam is discussed, and photographs are given which demonstrate this dependence in the cases of hydrogen, helium, and argon.The paper concludes by indicating the practical importance of the results given.

DOI:10.1049/jiee-1.1934.0161

出版商:IEE    

年代:1934

数据来源: IET

摘要:

An instability in synchronous machinery which cannot be assigned to variations in the load torque or driving torque is frequently experienced. This instability was shown by Hopkinson to be due to a negative damping coefficient which can, under certain circumstances, exceed the positive damping inherent in the machine and apparatus to which it may be connected. If this condition be achieved then any displacement from the normal running position will result in a sinusoidal vibration (about this position), increasing exponentially, until the machine either falls out of step, or (the coefficient of negative damping becoming modified by the effects of increasing displacement) settles down to a steady oscillation.In the first part of this paper the work of Rosenberg and Kapp is recapitulated to demonstrate the possibility of harmonic vibrations (about the normal running position) of alternators working in parallel. An expression is next derived for the damping coefficient of a synchronous machine in which the cross-magnetizing and demagnetizing coefficients are equal, and in which no damping grids are fitted. Some of the effects of armature reaction are ignored in this case. The conditions for instability are investigated.The theory is next extended to the case of a machine having unequal coefficients of cross-magnetization and demagnetization, and the effects of armature reaction are considered in greater detail. An expression for the damping torque is derived, and the conditions for negative damping are again investigated.Damping grids are then assumed to be fitted to the poles and in the interpolar spaces of the unsymmetrical machine last considered, and an expression for the damping torque is arrived at in which the armature resistance is as a first approximation neglected. This expression is compared with the torque equation of an induction motor to show how, upon analogy, the resistance of the grids for a damper of given performance may be calculated. An expression is also derived by which the negative damping due to the armature resistance may be assessed.In the section of the paper devoted to the consideration of experimental work, measurements are described which were undertaken to confirm the formulae obtained from mathematical analysis, and it is shown that fairly good agreement can be obtained between the measured and calculated magnitudes.The Appendices are concerned with the further elucidation of certain points in the mathematical treatment, and with the consideration of the positive damping inherent in synchronous machines, and in certain types of apparatus to which they may be mechanically connected.

DOI:10.1049/jiee-1.1934.0162

出版商:IEE    

年代:1934

数据来源: IET

摘要:

The paper discusses the mode of propagation of energy under steady current conditions, and advances the view that it is only a special case of radio transmission. The electromagnetic theory governs all electrical processes, but, while the high-frequency disturbances of light, or radio-telephony, move in waves which are known to retain their individuality when superposed, the principle of independence does not seem to be applied when the disturbances are of very low frequency so as to approach steady current conditions. In the last case the electromagnetic fluxes are, even nowadays, often regarded as static, and when such fluxes are superposed it is generally assumed that they merge into a single flux. Poynting's theorem of energy flow suggested that the fluxes due to steady currents are moving through the dielectric, but tacitly assumed that the fluxes form a single stream, and that nothing of the nature of reflection occurs when this stream reaches a material surface.It would seem only to harmonize with Maxwell's theory, and with the properties of light, if such streams when incident on matter were to give rise to reflected ones, and therefore to a system of superposed streams. The aim of the paper is to show that such a view is quite consistent with the known distribution of energy to the various parts of the conducting circuit.The mathematical problem is discussed in Part 2 of the paper. The analysis is an example of Heaviside's vector methods. It is necessarily based on assumptions. The physical aspects and the justification of these assumptions are dealt with in Part 1.

DOI:10.1049/jiee-1.1934.0163

出版商:IEE    

年代:1934

数据来源: IET

摘要:

This paper deals in a general manner with the electromagnetic forces exerted between current-carrying conductors. The factors introduced by the use of alternating current are taken into account and the effects upon the forces of conductor shape, current distribution, and proximity of inductive material, are considered. The characteristics of the forces, the reactions they produce, and the effects of resonance, are also examined.The results of the investigation are given either in general terms or in the form of equations, which are presented in a manner convenient for use in the calculation of electromagnetic forces on alternating-current circuits.

DOI:10.1049/jiee-1.1934.0164

出版商:IEE    

年代:1934

数据来源: IET