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Electrical Engineers, Proceedings of the Institution of

Issue 10 • Date October 1966

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Displaying Results 1 - 25 of 29
  • Charge-control analysis of m.o.s. and junction-gate field-effect transistors

    Page(s): 1565 - 1570
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (622 KB)  

    Useful expressions for the small-signal forward- and reverse-transfer parameters of metal-oxide-semiconductor and junction-gate field-effect transistors are derived from a simple unified charge-control analysis which is also applicable to the bipolar transistor. Basic parameters of field-effect and bipolar transistors are compared. It is shown that, although the physical mechanisms involved in the operation of these three types of transistor are distinctly different, their electrical equivalent-circuit representation and the significance of the associated parameters are identical. View full abstract»

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  • One- and two-way code translations using linked-list storage

    Page(s): 1571 - 1574
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (536 KB)  

    The paper describes two applications of the computer-programming technique of linked lists to code translators. The first application is to a dialling code to routing or charging digits translator, where the input and output have arbitrary complexity in terms of number of digits and number and length of translations. The second application is for number to equipment-number translation. It increase in storage requirements, at the cost a simple one-to-one translator, such as is used for directory-number to equipment-number translation. It is shown how two-way translations may be obtained, without increae in storage requirements, at the cost of restraining the complexity of the input or output code. View full abstract»

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  • Tolerance analysis of the superconducting continuous-sheet memory

    Page(s): 1575 - 1579
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (630 KB)  

    A simple tolerance analysis of the superconducting continuous-sheet memory predicts maximum tolerances, of ±14%, but higher tolerances have been measured. The analysis presented here considers the implications of some of the simplifying assumptions traditionally made. More detailed considerations can either increase or decrease the predicted tolerances. The justification of the usual current switching analysis is examined, and it is concluded that a maximum average energy-density switching criterion should be used but that critical current switching has the dubious though useful advantage of simplicity. Since calculated tolerances depend on the simplifications assumed, any conclusions regarding the ultimate feasibility of proposals for the continuous-sheet memory which are based on calculated tolerances are ill founded. There seems to be no fundamental reason why the measured operating tolerances cannot be increased beyond 14% if the fabrication processes and parameters governing them can be elucidated and controlled. View full abstract»

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  • Amplifiers using bipolar and unipolar transistors with limited drain-source voltage

    Page(s): 1580 - 1586
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (910 KB)  

    An important class of amplifiers uses a field-effect device in the first stage and a bipolar transistor in the second. If the drain-source voltage of the former is limited to the base-emitter voltage of the latter, a particularly simple circuit arrangement results. Other advantages of operation in this mode include reduction in the power dissipated in the field-effect device, improvement in high-frequency response and, when circuit constants are suitably chosen, some degree of inherent compensation for change of working conditions due to thermal effects. Of the four possible configurations which give high input impedance and voltage gain, it is shown that only two can easily be stabilised against working-point changes, and of these one [in which a common-drain (c.d.) amplifier precedes a common-emitter (c.e.) stage] is preferred, because it exhibits higher gain and lower output impedance and needs only a single polarity of supply voltage. The transfer conductance, input and output impedances and thermal drift of the c.d.-c.e. amplifier are calculated, using an equivalent circuit in which the drain-source channel is represented by a variable resistor. View full abstract»

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  • Four-terminal operation of m.o.s. transistors

    Page(s): 1587 - 1595
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    The charge induced in the channel of a silicon m.o.s.t. due to the capacitance of the depletion layer in the bulk material has a significant effect if the resistivity is less than about 10¿cm. With the substrate short-circuited to the source, the pinchoff voltage is reduced. The substrate provides a second control terminal, and 4-terminal operation is particularly useful if the fractional changes in voltage are limited so that the capacitance between the substrate and the channel is essentially constant. The drain current can be made to vary according to the sum of the signal voltages applied to the gate and the substrate. It is also possible to square this sum or to multiply it by a third signal voltage applied to both the drain and source in antiphase. With sinusoidal generators there is selective mixing. View full abstract»

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  • Investigation of high-frequency no-load losses in induction motors with open stator slots

    Page(s): 1597 - 1605
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1162 KB)  

    High-frequency components form a very important part of the no-load losses of induction motors having open stator slots. The paper presents the results of an experimental investigation which was designed to assess the effects on the losses of a variety of rotor design features. Twelve experimental rotors included three squirrel-cage types having, respectively, unskewed slots, skewed slots with uninsulated bars and skewed slots with insulated bars. A 3-phase wound rotor was tested for comparison purposes. The main conclusion is that, in rotors having skewed insulated bars or phase windings, the high-frequency core losses can be as large as the high-frequency I2R losses in unskewed rotors. The effect of variations in the bar-to-iron contact resistance Rq is large. The nature of this resistance was investigated separately, and it is shown that it is by no means a constant parameter. High-frequency stator core losses were also investigated, using search coils, and these are shown to be of importance only with unskewed cage rotors, and also possibly with phase-wound rotors with wide slot openings. The experimental results are compared with theoretical calculations, including the effect of bar-to-iron resistance. View full abstract»

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  • Analysis and measurement of radial power flow in machine air gaps

    Page(s): 1607 - 1615
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    The theory of radial power flow in a machine air gap is developed, with emphasis on the powers associated with individual harmonic effects and on the practical possibility of measuring these powers. The analysis is made in terms of travelling-wave modes in the air-gap annulus and leads to an alternative Poynting vector which is convenient for measurement. Some important analytical results relate to the simple measurement of axially nonuniform fields. The general construction of a measuring probe is described, and some experimental results on the measurement of synchronous power illustrate its effectiveness. The air gap offers a potential advantage for the direct measurement of individual harmonic loss, compared with either the stator or rotor region. More generally, the rigorous analysis in terms of wave modes and the discussion of their associated power flows forms an instructive and stimulating view of machine operation. View full abstract»

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  • Note on induction-machine performance with a variable-frequency supply

    Page(s): 1617 - 1623
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    Previous work on the variable-frequency performance of induction machines is reviewed, and, for completeness, references to other aspects of transient performance are included. It is shown that results based on the analysis of constant-current performance cannot be expected to correlate well with actual performance under forced-voltage conditions. Attention is drawn to the simplicity of the direct solution of the complete set of 2-axis equations for variable-frequency variable-voltage conditions, and appropriate methods of solution by digital and analogue computer are outlined. These methods are used to study briefly the factors influencing machine stability and improved techniques of achieving rapid speed changing. In connection with stability, using frequency-response and step-response tests, it is shown that parameters of special interest are operating frequency, rotor resistance and inertia. In particular, it is shown that there is an operating frequency for which damping is a minimum. In connection with speed changing, it is shown that continuous (rather than step) variations in frequency lead to quicker speed changes with lower current requirements. In the case of speed reversal, the method eliminates the disadvantageous feature of plugging, namely that rotor kinetic energy is dissipated as heat in the winding. View full abstract»

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  • Discussion on ¿Electricity for grain drying¿

    Page(s): 1624 - 1627
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  • Composite polar characteristics in multizone systems of phase-comparison distance protection

    Page(s): 1631 - 1642
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    The static distance-protection schemes now in use are based on 2-input relays that respond either to the relative amplitudes of the two input relaying signals or to the phase displacement between them. Both kinds of response afford a range of relay polar characteristics, but this may be considerably increased by extending the basic modes of comparison from which the characteristics may be derived. Of the two different comparison techniques, the paper is devoted to that of phase comparison rather than amplitude comparison, and its scope is extended by using more than two relaying signals to contribute to the comparison, by varying the angular limits of comparison, and by using two or more comparators in combination. The purpose of the paper is to examine possible applications of these forms of relaying in complete 3-zone protection schemes incorporating directional-reactance and mho characteristics and also the more recently derived family of discontinuous characteristics. In a 3-zone scheme of static protection, three or more signals may be conveniently arranged to effect phase comparison by combining, in relays extended to receive more than two signals, the signals that are ordinarily present in pairs at the relay inputs in the different zones. It is shown how, in this way, a directional-reactance characteristic may be derived from a single multi-input relay simultaneously energised by the zone-1 and zone-3 relaying signals of a conventional 3-zone reactance scheme, thereby avoiding the use of reactance and mho starting relays in combination. In a similar way, it is shown that the long-reach zone-3 characteristic of a 3-zone mho scheme may be shaped by a 3-input comparison method to increase its discriminating margins against load encroachments on high-capacity transmission circuits. Other combinations of zone characteristics are given where alternative forms of control may be desirable in meeting different requirements. View full abstract»

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  • Investigation into new designs for h.v. insulators using synthetic materials

    Page(s): 1643 - 1648
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    Investigations into the application of some new materials to h.v. insulation are reported. The first is concerned with the exploitation of the properties of epoxide resin¿its mechanical strength, ease of casting, excellent electrical characteristics and high thermal conductivity. Two basic types of equipment were studied: the post insulator, which principally utilises the mechanical strength of the resins, and the h.v. bushing, which uses the facility of casting the material in large complex shapes and its high thermal conductivity. A second investigation was aimed at exploiting the extremely high tensile strength of plastic bonded glass-fibre rod, which exceeds that of mild steel, so that suspension insulators were the obvious application, and insulating crossarms were an alternative application. Work is not yet completed on either of these two investigations, but sufficient has been established to form a basis for a much wider exploitation of these materials. View full abstract»

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  • Considerations of the suppression of insulator flashover by resistive surface films

    Page(s): 1649 - 1653
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    It is well known that resistive glazes on porcelain insulators give a `voltage-stabilisation¿ effect, and improve the performance of such insulators when operated in polluted atmospheres. However, the mechanism of this stabilisation has not been made clear to date, because of the complexity of the problem. A qualitative assessment of some of the mechanisms which may contribute towards the improved performance is made, using a simplified insulator model. It is found that the presence of a stabilising glaze has no effect upon the stress at which a discharge propagates along the insulator surface, and that the effect of the glaze must therefore be to inhibit the formation of discharges. View full abstract»

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  • Design of the a.c. servomotor

    Page(s): 1657 - 1669
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    The modern servomotor is required to meet a stringent performance specification. This specification is shown to present basic design restrictions. In addition, manufacturing limitations and techniques provide extra restrictions on the design. The approximate design will be modified towards an optimum which is defined by quantities detailed in the specification. A general theory can be developed in terms of primary machine dimensions which will provide performance equations. These equations allow comprehensive design curves to be computed, which exhibit the effect of variation of all the normal design parameters on motor performance. The final design will be chosen by the designer from a range of possibilities made apparent from the curves. This choice will be dictated by such practical considerations as ease of construction, cost and availability of construction materials. View full abstract»

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  • Precision temperature control

    Page(s): 1671 - 1677
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    The problems associated with accurate control of temperature are discussed, and the various types of temperature-sensitive elements considered. It is shown that the thermistor offers greatest sensitivity and stability. The criteria underlying the design of a temperature-sensitive bridge using a thermistor are analysed. Details of the mechanical arrangements necessary for the close control of temperature of a volume of liquid are given, together with the design of the associated control equipment. The results of tests using the complete controller are presented, and they show that stabilities considerably better than ±0.0005°C. over a period of several hours are attainable for a volume of approximately 0.5 ft3, without recourse to excessive stabilisation of the ambient temperature. These results are reproducible over a temperature range of 20¿50°C. View full abstract»

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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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