摘要:

Tensor analysis is used to develop a comprehensive theory of the double induction regulator. The general case of a biased double regulator with completely dissimilar component single regulators is first examined. Working equations and equivalent circuits for other types of double regulator are then derived from those of the general case. Tests made on a simple (unbiased) double regulator are shown to agree closely with the behaviour predicted by theory.

DOI:10.1049/pi-c.1957.0012

出版商:IEE    

年代:1957

数据来源: IET

摘要:

Existing methods of representing saliency on network analysers are discussed. These include combined-reactance methods and two methods using a d.c. signal to represent the e.m.f. of the synchronous machine.A simple method of representing saliency, in association with a network-analyser generator unit, is then described, together with the associated electronic circuits. The results of a problem involving saliency, which has been solved by means of the apparatus described, are presented and the results are discussed.It is concluded that the method employed is more economical than those previously published, and is well within the normal limits of accuracy for electrical power-system analysis.

DOI:10.1049/pi-c.1957.0013

出版商:IEE    

年代:1957

数据来源: IET

摘要:

A rough field plot ascertained graphically can be used as the basis of a computational method of considerable accuracy. The plot is replaced by a net of orthogonal trajectories without sudden breaks of direction, the individual meshes being bounded by arcs of circles or straight lines. With the nodes of this net as the junction points of conductances, the 2-dimensional continuum within the problem boundaries can be converted into a network of lumped conductances. This network is analysed by measurement or computation.The paper deals with the graphical and computational layout of a net whose contours follow the assumed trajectories closely, and explains the graphical and computational determination of the lumped conductances. A large number of formulae and computing routines are derived, making possible the employment of semi-skilled workers or computing aids. The determination of the gradient and other special problems, such as computing the areas associated with Poisson's equation or dealing with sharp corners, are discussed and the relevant formulae are given.The advantages of the method, compared with the use of regular or irregular nets with straight-line inter-mesh boundaries, lie in the considerable reduction in the number of meshes for the same accuracy, and in the possibility of fitting the problem boundaries very closely. Two practical examples are given: using 4 × 6 meshes, the field gradient at the surface of an edge rounded by a non-circular curve is ascertained accurately within 0.6%; using 2 × 2 meshes, the cut-off frequency of the H11mode in a circular waveguide is determined with an error of less than 1.6%; this is an eigenvalue problem.

DOI:10.1049/pi-c.1957.0014

出版商:IEE    

年代:1957

数据来源: IET

摘要:

Governing in electric power systems by time-error provides a method of control with many advantages over speed governing, particularly if a high value of governor gain is used. The paper describes the operating results of a time-governed miniature system, the design the governor for stable operation and the associated tie-line controllers.

DOI:10.1049/pi-c.1957.0015

出版商:IEE    

年代:1957

数据来源: IET

摘要:

The paper presents merely one aspect of the general problem of propagation over a coastline, but special consideration is given to it since it differs from other effects in being present only at oblique incidence. By adopting a model for the coastal region the analysis given in Part I of the paper (see page 43) may be used to provide expressions for the angle of refraction appropriate to various positions of the transmitter and receiver relative to the coast. It is shown that the onset of the refraction occurs abruptly at the coastline, the theory suggesting that the direction of propagation is initially turned through an angle π/2. Within a wavelength of the coast, however, the refraction depends critically upon the way in which it is defined, and expressions which are equivalent at larger distances here lead to widely differing values. Nevertheless, if the transmitter is far away, it is certain that the refraction is largely confined to within a few wavelengths of the discontinuity and, moreover, decreases as the receiver recedes from the coastline; ultimately the original direction of propagation is restored. But, if the transmitter is itself within the coastal region, there is a permanent distortion of the field and a directional error which is virtually independent of the position of the receiver.

DOI:10.1049/pi-c.1957.0016

出版商:IEE    

年代:1957

数据来源: IET

摘要:

Strain-energy methods have been used to study the mechanical behaviour of cat's-whiskérs in semi-conductor devices, and the condition for zero transverse contact pressure and deflection has been expressed in the form ∫0Lxy/Idl=0, wherexandyare parameters which define the shape of the whisker andIis the moment of inertia of the whisker cross-section. For wire whiskers this is equivalent to ∫0Lxydl= 0. The theory is perfectly general, and can be applied to plane whiskers of any shape. Formulae have been derived for calculating components of pressure and deflection parallel with and normal to the crystal face. Experiments on large-scale whisker models have shown close agreement with the theory.

DOI:10.1049/pi-c.1957.0017

出版商:IEE    

年代:1957

数据来源: IET

摘要:

A simple method is presented for the rapid calculation of cyclic rating factors for cables laid direct in the ground and cables in ducts. The method may be applied without difficulty even in the case of complicated load curves, but for single-peaked load curves the calculation is especially simple. Tables of relevant functions are included as are additional tables of parameters for cables conforming to B.S. 480: 1954. Examples are given illustrating the ease and speed of the proposed method, together with the variation of cyclic rating factors with soil thermal constants.

DOI:10.1049/pi-c.1957.0018

出版商:IEE    

年代:1957

数据来源: IET

摘要:

After a brief reference to the impossibility of producing a sinusoidal flux-wave with the more common forms of synchronous generator, the paper deals with the conditions necessary for a sinusoidal flux-variation in inductor-type alternators.

DOI:10.1049/pi-c.1957.0019

出版商:IEE    

年代:1957

数据来源: IET

摘要:

A process for the growing of quartz crystals artificially is briefly described. This so-called synthetic quartz, which is being grown reproducibly as well-formed crystals weighing about 135 grammes, possesses electrical and mechanical properties which closely follow those of the natural Brazilian quartz commonly used for piezo-electric purposes. The high overall quality of synthetic quartz, its freedom from twinning and other faults and its regular shape and size make it a convenient material to handle with the minimum of wastage.Measurements have been carried out to compare the properties of oscillator crystals cut from natural and synthetic quartz. The behaviour of the AT- and BT-cuts has been investigated thoroughly, while some results have also been obtained on units of the CT-, DT-and 5° X-cuts. Most of the parameters measured show no appreciable difference between the values for natural and synthetic quartz. Two notable exceptions are a small difference in the frequency/temperature characteristics of AT-cut units, whether operated at fundamental or at overtone frequencies, and an apparently reduced activity of face-shearmode units of the CT-and DT-cuts from the synthetic material.The significance of these results is discussed, together with the possibility of more accurate measurements to compare the intrinsic mechanical losses in natural and synthetic quartz.

DOI:10.1049/pi-c.1957.0020

出版商:IEE    

年代:1957

数据来源: IET

摘要:

It is shown that the effect of magnetic saturation on the d.c. dynamic braking characteristics of a.c. motors can be determined by a mathematical method of analysis which uses the net value of the equivalent alternating magnetizing current, rather than the fractional speed, as the independent variable of functions expressing the values of the braking torque and secondary-circuit current. The method is applicable to both asynchronous and synchronous polyphase machines, and to asynchronous single-phase motors. It is noted that the deep-bar type of squirrel-cage induction motor, in which the rotor resistance varies appreciably with the rotor speed, does not present any special difficulty in the application of the method.A quantitative relationship is derived for the maximum-torque conditions. The variation of the maximum torque, and of the criticalspeed/secondary-resistance ratio, with the direct primary current is determined for values of the latter up to four times the rated primary current, and with zero, normal and excessive values of secondary reactance. It is shown that even when the existence of the normal reactance only is neglected, the maximum torque may be in error to the extent of 16%. Still greater errors arise from the neglect of magnetic saturation, even with the direct primary current limited to the rated value.It is shown, also, that the torque/resistance characteristics may be derived directly from the torque/speed characteristics.

DOI:10.1049/pi-c.1957.0021

出版商:IEE    

年代:1957

数据来源: IET