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Electrical Engineers, Proceedings of the Institution of

Issue 3 • Date March 1969

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Displaying Results 1 - 25 of 39
  • Silicon-carbide electroluminescent devices

    Publication Year: 1969 , Page(s): 329 - 333
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (747 KB)  

    Electroluminescent devices have been constructed from epitaxially grown p-n junctions in silicon carbide. By suitable choice of material polytype and impurities, the luminescence can be controlled, to give various colours covering most of the visible spectrum. Brightnesses in excess of 100ft L (342cd/m2) at current densites of 10A/cm2, have been achieved. The lamps operate at a few volts d.c. and 10¿100mA, but pulsed operation at higher currents is possible, and the devices will respond to pulses with rise times below 1µS. Operating lives in excess of 15000h have been obtained at 50mA, with a constant light output. Arrays of lamps fabricated on a single crystal have been found suitable for applying information to photographic film, and as numerical displays. The luminescence intensity of these devices is, generally, proportional to input current, and the area of luminescence remains substantially constant. However, by adding a third electrode to the structure, it is possible to control the area of luminescence of the device with suitable biasing. These devices have applications as magnitude and tuning indicators. View full abstract»

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  • Focusing aid for an electron microscope

    Publication Year: 1969 , Page(s): 334 - 338
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (668 KB)  

    An aid to focusing an electron microscope is described, employing the signal obtained by scanning the image. It is shown that use can be made of certain frequency components from the resulting signal, in order to provide an indication of the focus condition. A voltage is generated which is proportional to the mean power of these frequency components, and which, for most objects, has an extremum value at focus. The greatest sensitivity is obtained when phase-contrast effects are present, when the above voltage has a minimum value at focus. An experimental system has been built using a selenium electron-bombardment-induced-conductivity (e.b.i.c.) target scanned by a conventional raster, and, although targets of less than the highest quality were used, it has been shown that typical biological specimens, exhibiting phase contrast, can be focused with a reproducibility greater than is possible by eye. Simple theory predicts that, for such objects, all frequency components are equally useful as a measure of focus, but practical results show that only the upper half of the spectrum should be used, the lower frequencies tending to give rise to error in the direction of over-focus. The arrangement has also been used, in conjunction with a peak-holding controller, in an automatic focusing system. View full abstract»

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  • New all-electrostatic vidicon

    Publication Year: 1969 , Page(s): 339 - 347
    Cited by:  Papers (3)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1265 KB)  

    A new, all-electrostatic vidicon has been developed, in which crossed planar lenses are used to focus the electron beam sequentially in the frame and line directions, instead of the rotationally symmetrical lenses used in present-day electrostatic vidicons. The arrangement is the equivalent of crossed cylindrical lenses in light optics. Such planar lenses can be formed between two pairs of parallel plates. The second pair of plates of each lens is also used for scanning. By introducing a fine mesh in the plane of symmetry of a 2-element lens, one pair of plates may be omitted, thus increasing the focusing power of the lens and making it shorter. A computer program was written to plot electron trajectories. The computed results, together with experiments made on a scaled-up demountable gear and with sealed-off tubes, were used to optimise the design. In the course of the work, it was found that the image of a crossover, rather than that of a physical aperture in the electron gun, gave a focused spot more suitable for this particular application. The modulation depth of a 400 TV line pattern of black and white bars (i.e. 400 lines per picture height) is approximately 40% in the centre and 25% in the corners. Occasionally, over 50% modulation has been achieved in the centre. A remarkable feature is that the image field is practically flat. The geometrical fidelity is correct to within ±0.25% over the whole scanned area, is even better in the quality area in the centre, and is very uniform from one tube to another. This makes this type of tube highly suitable for the registration required in colour cameras. View full abstract»

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  • Construction and performance of practical field emitters from lanthanum hexaboride

    Publication Year: 1969 , Page(s): 348 - 350
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (366 KB)  

    The use of field emitters in conventional vacuum devices has been retarded by the technological difficulties associated with the manufacture of reproducible points having a long life. In this paper the construction and performance of emitters from single crystals of lanthanum hexaboride are described and discussed. The results indicate that these emitters are capable of a significantly better performance than other known emitters, and can operate at current densities exceeding 105 A/cm2 for many hundred hours at residual-gas pressures of 10¿9 torr. View full abstract»

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  • Temperature effects in glow-discharge tubes

    Publication Year: 1969 , Page(s): 351 - 354
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (420 KB)  

    Glow-discharge reference tubes with various cathode materials, but identical gas filling and pressure, operating in the normal-glow mode, show different temperature coefficients when operated under similar conditions. Measured temperature coefficients are compared with calculated values obtained from a knowledge of the running-voltage/current characteristics at different pressures and temperatures. An existing theory is shown to hold for all the combinations of gas filling, geometrical construction and cathode material examined, and the differences in temperature coefficients are attributed to the uniqueness of the running-voltage/pressure curve for each particular gas-filling/cathode-material combination. A theory is proposed which enables the temperature coefficient of a tube operated with anode fall to be estimated from a knowledge of the running-voltage/current characteristic at different pressures and temperatures. Good agreement was obtained between measured and calculated values. View full abstract»

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  • Switch using bipolar transistors for use in analogue computing

    Publication Year: 1969 , Page(s): 355 - 364
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (933 KB)  

    In this paper, a transistor switch for use in analogue-computing circuits is described, and the essential steps in its design are given. The switch is then applied, in a feedback configuration, to produce a fast, accurate method of resetting the initial conditions of an integrating computing amplifier. An assessment of the steady-state errors is provided, and a detailed transient analysis leads to the prediction of reset transients for both transistor and valve operational amplifiers. These transients are confirmed experimentally. It is shown that the switch leads to a cheap and accurate way of resetting integrators, which will allow solid-state analogue machines to be operated repetitively at rates of over 1 kHz. View full abstract»

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  • Superdirective aerial array containing only one fed element

    Publication Year: 1969 , Page(s): 365 - 372
    Cited by:  Papers (2)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (947 KB)  

    The maximum-gain theorem developed by Bloch, Medhurst and Pool in 1953 has been applied to an endfire array of four unequally spaced half-wave dipoles, an extensive range of element spacings being taken. A configuration has been found where, for maximum gain, one element is parasitic and two may be joined passively to form a parasitic pair, leaving one element to be fed. Two such arrays designed to operate at 275MHz have been built with ¿in- and ¿in-diameter elements, respectively. The theoretical maximum gain for such arrays is about lOdB, and gains of 9.0dB and 8.8dB were measured for the two experimental arrays. Of the discrepancy, 0.2dB and 0.1 dB, respectively, were calculated to be due to losses in the metal structure (i.e. the dipoles and the section of transmission line connecting the parasitic pair). An orthodox endfire array (having currents of equal amplitudes, phased so that the distant fields add in the direction of maximum gain) of the same size would have a gain 5¿dB less (3¿: 1 in power). A Yagi array with the same gain would need to be between 2¿ and 3¿ times longer, depending on its design. View full abstract»

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  • 17.5 ft-long multiconical taper for TE01 mode in 29.7 in-diameter waveguide at X band

    Publication Year: 1969 , Page(s): 373 - 376
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (637 KB)  

    An X band TE01-mode taper to connect circular waveguides with diameters of 2.25 and 29.7 in was designed, fabricated and evaluated. The 29.7 in circular aluminium waveguide for the TE01 mode had an attenuation of 2.1 × 10¿6dB/ft at 8.35GHz. To obtain a taper of short length that would be economical to fabricate, a multiconical type was selected. The four mode-converting junctions in the multiconical taper were designed to cancel the first higher-order TE02 mode. The taper was 17.5 ft long and comprised 12 sections. The larger-diameter sections were fabricated by using a thin sheet of aluminium alloy, rolled and longitudinally welded. Circular flanges and stiffening rings provided the desired degree of circularity. By using a spinning dipole mode analyser, the TE02 and TE03 modes due to the taper were measured to be about 25 dB below the TE01 mode. View full abstract»

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  • Effects of noise contributed by t.r. devices on low-noise receivers

    Publication Year: 1969 , Page(s): 377 - 382
    Cited by:  Papers (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (930 KB)  

    The deleterious effects on the noise factor of a receiving system of inserting a t.r. device immediately before a quiet microwave amplifier are investigated. The noise contribution of the device is separated into its component parts, each of which is examined of its contribution to the degradation of the receivingsystem noise factor. In addition, the noise factor of the t.r. device is determined, independent of interconnecting components. A technique to measure excess noise energy is presented, from both an analytical and practical viewpoint. It is shown that an independent determination of noise factor, and relative gains of signal and image frequencies of the test receiver, are not necessary when measuring igniter noise ratio. View full abstract»

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  • North Staffordshire Sub-Centre: Chairman's address: The history of submarine cable links

    Publication Year: 1969
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (162 KB)  

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  • Optimisation of bandwith in noniterative wideband amplifiers

    Publication Year: 1969
    Cited by:  Papers (1)
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  • Correlation of the air-gap vector potential of an induction motor with the magnetising current

    Publication Year: 1969 , Page(s): 385 - 390
    Cited by:  Papers (2)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (670 KB)  

    As a preliminary to any attempt to unify the field and circuit theories of rotating electric machinery, it is necessary, if possible, to develop a one-to-one relationship between a field quantity and a circuit quantity. In the paper, Maxwell's equations are applied to the slip-ring induction motor using homogenised permeabilities in the stator and rotor slotted regions. The mathematically exact solution is checked by reference to a conventional design. A simple and approximate solution is derived, and is found to be essentially the same as the normal design treatment. The air-gap vector potentialA is shown to be related to the current i which produces it, by the simple formula A=6/¿3 T/¿LS i sin ¿¿ where T is the number of turns per phase, ¿ the number of pole pairs, L the axial length, and S, for which an expression is given, the reluctance per pole-pitch. View full abstract»

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  • Eddy-current and hysteresis effects in rotating machines

    Publication Year: 1969 , Page(s): 391 - 394
    Cited by:  Papers (10)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (656 KB)  

    Hysteresis in the magnetic circuit of a rotating machine is represented by an approximate method which neglects harmonics and enables the hysteresis motor to be analysed by the equivalent Kron primitive machine. The method is extended to hysteresis and eddy-current effects in hysteresis, induction and synchronous machines; steady-state equivalent circuits are derived for the hysteresis motor and induction machine. View full abstract»

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  • Discussion on "Lightning performance of British high-voltage distribution systems"

    Publication Year: 1969
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  • Discussion on ¿Gas-turbine plant for peak-load generation and synchronous compensation¿a review of the installations for CEGB¿

    Publication Year: 1969 , Page(s): 396 - 398
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  • Discussion on ¿Cables for aircraft¿

    Publication Year: 1969 , Page(s): 399 - 402
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  • Discussion on "Modern transmission-line maintenance"

    Publication Year: 1969
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  • Generalised electrostatic-machine theory

    Publication Year: 1969 , Page(s): 403 - 405
    Cited by:  Papers (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (257 KB)  

    Field theory suggests that duality exists between electrostatic and electromagnetic machines. Circuit theory is used to develop a generalised electrostatic-machine theory as a dual of the generalised electromagneticmachine theory. Various electrostatic machines are shown in their primitive forms, and their electromagnetic counterparts are suggested. View full abstract»

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  • Discussion on ¿Aluminium conductors for overhead lines¿

    Publication Year: 1969
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  • Fundamental-frequency eddy-current loss due to rotating magnetic field. Part 1: Eddy-current loss in solid rotors

    Publication Year: 1969 , Page(s): 407 - 410
    Cited by:  Papers (2)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (470 KB)  

    The flux penetration in solid ferromagnetic cores is analysed without using the simplifying assumption that the B/H curve is a straight line, or a limiting step function. The nonlinear variation of the fundamental B1/H curve is included in its entirety by substituting the equation B1 = KH1¿2/n, which fits the magnetisation curve very well, especially beyond the knee portion. The theory is applied to induction motors with solid-iron secondaries, and solutions are obtained for flux and current densities, rotor power factor and eddy-current loss. Simplified expressions are given for easy numerical calculation. Substitution of n = 2 in the equations leads to results which have already been obtained in previous literature using the limiting B/H curve. Results of experimental work carried out on a solid-rotor induction motor are also presented. Curves are given to obtain the eddy-current loss per unit surface of any given solid rotor, operating at any given slip, and with any surface magnetising force. This virtually eliminates numerical calculations when the theory is applied to a new solid-rotor machine. View full abstract»

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  • Fundamental-frequency eddy-current loss due to rotating magnetic field. Part 2: Eddy-current loss in hollow rotors

    Publication Year: 1969 , Page(s): 411 - 414
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (453 KB)  

    A nonlinear analysis is given for the flux penetration in hollow ferromagnetic cores. The fundamental magnetisation curve is represented by the equation B1 = KH1¿2/n. Graphical correlations are given to eliminate lengthy numerical calculations. For a given core of finite depth subjected to a surface magnetising force of known frequency, the total current, flux, eddy-current loss etc. can be readily obtained by a reference to these graphs. The theory is applied to induction motors with hollow rotors, and the results of experimental work on such a motor are presented. View full abstract»

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  • Western Supply Section: Chairman's address. Developments of the h.v. transmission system in the south-west of England

    Publication Year: 1969
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (159 KB)  

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  • Radio interference from high-voltage insulators under direct-voltage conditions

    Publication Year: 1969 , Page(s): 415 - 421
    Cited by:  Papers (2)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (788 KB)  

    A laboratory investigation into the radio interference arising from electrical discharges on porcelain pin insulators and string insulator units (cap-and-pin type) under high, direct-voltage conditions is described. The effects of the magnitude and polarity of the applied voltage, the surface conditions of the insulators, and the relative humidity of the air, have been studied and phenomena compared with those observed under alternating-voltage conditions. Measurements have been made in the frequency range 0.15¿30 MHz, and details of the techniques adopted are given. It has been shown that radio interference is much lower with direct voltages than with alternating voltages of the same peak value. View full abstract»

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  • North Midland Power Section: Chairman's address. Some experiences in the testing of h.v. insulation in service

    Publication Year: 1969
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  • North-Western Supply Section: Chairman's address. Total power systems in the 1970s and¿

    Publication Year: 1969 , Page(s): 423 - 424
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Aims & Scope

The Proceedings of the Institution of Electrical Engineers was published by the IET between 1963 and 1979.

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