摘要:

The topological rules for the calculation of a signal-flow-graph transmittance are usually proved by quite a lengthyad hocargument. This is neither necessary nor advantageous because a straightforward matrix analysis of the problem leads directly to the desired result. Such an analysis is given in the paper.

DOI:10.1049/pi-c.1962.0011

出版商:IEE    

年代:1962

数据来源: IET

摘要:

The method of images is widely used in the analysis of fields due to currents and charges, but it is of limited application and a more general method is required. It is the object of the paper to show that, for the analysis of 2-dimensional fields due to linear filaments of current or charge, conformal-transformation methods can be used simply for a very wide range of problems; the only requirement is the determination of an equation (or a series of equations) which transforms a straight line into the shape of the boundary of the field. The boundary types which can be treated simply are equipotential, flux-line, and combinations of the two. The necessary basic field solutions for each of these three types, for fields interior and exterior to given boundaries, are developed.Use of the method is demonstrated with two examples involving simple polygonal boundaries. The first is a determination of the error caused by treating a finite boundary as if it were infinite (an approximation frequently necessary when the image method is used). The second is an estimation of the inductance of a conductor carrying high-frequency alternating current and influenced by a conducting surface. A method of estimating the inductance of a conductor influenced by permeable bodies is also mentioned.

DOI:10.1049/pi-c.1962.0012

出版商:IEE    

年代:1962

数据来源: IET

摘要:

Equivalent electrical networks to represent fields described by certain partial differential equations have for many years been used as a standard analogue technique. In these networks the dependent and independent variables are usually represented by voltage drops and currents in the branches, called ‘across’ and ‘through’ variables, and these analogue quantities on the network give the distribution of the field.In setting up equivalent networks for this purpose Kron added two steps to the existing concepts, namely (i) he derived circuits in terms of general co-ordinates, the topology of each network being independent of the co-ordinate system chosen, and (ii) by applying Stokes's theorem to the system of vectors he showed that the networks thus derived could be interpreted as containing the field quantities flowing in the filled space. The quantities measured on the network then correspond to line, surface or volume integrals of the vector field quantites. With this interpretation the networks become more realistic models of the fields since the whole space is filled and the choice of co-ordinate system does not affect the physics of the phenomena.The present paper describes the mathematical basis of this fuller interpretation of analogue networks.

DOI:10.1049/pi-c.1962.0013

出版商:IEE    

年代:1962

数据来源: IET

摘要:

Relationships between the maximum power gain and the internal loop gain of a general linear two-port network are developed. A new stability factor is defined from the maximum-gain potentiality of the network without external feedback, and is physically identifiable as the modulus of the internal loop loss (the inverse of loop gain) at maximum available power gain where this is finite. Several theorems on this loop gain show the relationships between the new stability factor, Stern's stability factor and the author's ‘performance factor’.Though the earlier factors may be obtained by constraints on the internal loop gain, they are shown not to be exactly related to the internal loop gain of the two-port network at maximum power gain; also, they are not exact invariants in matrix environments save in exceptional cases. The new stability factor is an exact invariant for all its values in the possible matrix environments, demarcates the regions of potential instability and absolute stability, and is directly related to the maximum available power gain of the two-port network, when this gain is finite.

DOI:10.1049/pi-c.1962.0014

出版商:IEE    

年代:1962

数据来源: IET

摘要:

The rapid changes in flux distribution, which occur as a slotted armature moves relative to a pole corner, give rise to losses both in the copper and in the iron. These flux pulsations can have a considerable effect on the performance of both a.c. and d.c. machines.The author presents an accurate determination of the field of a slot passing under a rectangular pole corner, and the flux changes under relative motion are calculated over the range of dimensions of practical interest. The flux entering the armature slots is calculated and compared with values measured by search coils; the two sets of results are in close agreement. The effect of the slot width on the induced e.m.f. in the armature conductors is commonly ignored in design work. However, the effect is shown to be appreciable. Finally, the variation in the forces acting on the armature teeth is determined; this quantity is exceedingly difficult to obtain experimentally.

DOI:10.1049/pi-c.1962.0015

出版商:IEE    

年代:1962

数据来源: IET

摘要:

A study is made of the theoretical signal/noise gain of an ideal strip transducer; this gain is the actual signal/noise ratio compared with that for a ‘point’ receiver (i.e. one whose dimensions are small compared with the wavelength at the lowest significant frequency). The results are not restricted to narrow-band systems and relate generally to noise fields which may be non-isotropic and have non-uniform frequency spectra. The theory is used to investigate the correlation between the noise outputs of the various sections of a subdivided transducer, and it is shown that, at least in the narrow-band case, the usual assumption of negligible correlation is generally justified in practice. Multiplicative systems are also considered, and it is shown that, in certain circumstances, the overall signal/noise ratio of such a system may be better than that of either of its component groups. The results obtained are also generally applicable to ideal radio receiving arrays.

DOI:10.1049/pi-c.1962.0016

出版商:IEE    

年代:1962

数据来源: IET

摘要:

A method for realizing pulse-like time functions by means of 4-terminal networks developed on the basis of equivalence to delay lines is presented. Illustrative arrangements based on this method for generating pulses of the forms sint, sin2t, sin3t, etc., are described. A method of synthesis of networks for generating specified pulse forms is also suggested. Some experimental results are presented.

DOI:10.1049/pi-c.1962.0017

出版商:IEE    

年代:1962

数据来源: IET

摘要:

Owing to the difficulty in the direct measurement of temperature in the winding and steel of turbo-alternator rotors, indirect methods, requiring a knowledge of the boundary conditions, can be used to advantage. In the present work the electrical-analogue approach is used, i.e. the replacement of thermal quantities by analogous electrical ones, giving both steady-state and transient solutions. The latter is of interest when considering overload capacity and unbalanced loading.The rotor studied was that of a 60 MW 3000r.p.m. 11kV 50c/s turbo-alternator with indirect cooling by hydrogen at a pressure of 41b/in2(gauge). Design and constructional features of a resistance-capacitance analogue representing two-dimensionally the thermal conditions in a ‘slice’ of rotor 1 in thick and containing the hottest slot are given. By simple adjustment any slice in the rotor length may be simulated. Incorporated in the analogue are electronic current-input units which vary the ‘copper-loss’ input currents to allow for the change in winding resistance with temperature.Transient temperature rises at 20 points in and around the hottest slot in sections at the rotor end and at the axial centre are obtained for the application of step-functions of excitation currents of 500 A and 550 A and various values of surface loss. The mean winding temperature obtained is compared with that measured on the actual machine using the change-of-resistance method and good agreement is found. Variations in the coolant temperatures are seen to have small effect on the analogue temperature-rises.

DOI:10.1049/pi-c.1962.0018

出版商:IEE    

年代:1962

数据来源: IET

摘要:

The donor element in the oxide matrix is now regarded as strontium metal, and in the present Part its movement in an electric field is considered. It is shown experimentally that the donor is positively ionized, can be chemically isolated by solution in a platinum cathode core, is mobile in an electric field at temperatures above 550° K, and is incapable of diffusion in a concentration gradient below 800° K. Excessive concentration of the positive ion is shown to give rise to a dramatic increase in matrix resistivity. It is finally concluded that there exists an optimum donor concentration at which the conductivity of the matrix is at a maximum.

DOI:10.1049/pi-c.1962.0019

出版商:IEE    

年代:1962

数据来源: IET

摘要:

The transform method for evaluating the coefficients of the various terms in the output autocorrelation function of a non-linearity with an input consisting of a sinusoidal signal and Gaussian noise is considered. Solutions, all of which involve confluent hypergeometric functions, are given for a few analytically defined non-linear characteristics. A short table of these functions is also given to facilitate computation. A new expression for evaluating the coefficients, a double integral involving the non-linear characteristic and the moments of the sinusoidal and Gaussian input signals, is derived. A graphical method of solution applicable to any single-valued non-linearity is given, and a comparison made, with experimental and theoretical results. Extension of the technique to several uncorrelated input signals of any known amplitude probability density distribution is shown to be possible.

DOI:10.1049/pi-c.1962.0020

出版商:IEE    

年代:1962

数据来源: IET