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Electrical Engineers, Proceedings of the Institution of

Issue 8 • Date August 1967

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Displaying Results 1 - 25 of 34
  • Experimental data on X band surface waveguides and launchers

    Page(s): 1021 - 1029
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1088 KB)  

    The paper describes some investigations which have been carried out into the behaviour of dielectric-coated wires used as surface waveguides at Xband frequencies. The decay coefficient of the radial external field strength has been determined for several wires, and the corresponding attenuation coefficient has been calculated. The design of a suitable surface-wave launcher is also discussed, and the performance of such a launcher in the frequency band 8.6¿9.84Gc/s is described. All investigations were carried out in laboratory conditions. View full abstract»

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  • Effect of degenerate E11ν mode in H01ν mode cavity on the measurement of complex permittivity

    Page(s): 1030 - 1034
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    The paper discusses measurements of the relative permittivity and the loss angle (tan δ) of a material using the resonance method. The resonator used was a cylindrical cavity in which the dominant-mode excitation was H01ν. The cross-section of each sample had a radius equal to the internal radius of the cavity, and the measurements were made with sample thicknesses ranging from one wavelength to a small fraction of a wavelength. Using circular coupling holes in the top surface of the cavity of the type described by Bleaney,2 it was found that, over the range of sample thicknesses considered, the measured permittivity and tan δ showed a periodic variation, the total spread being 2% and 42%, respectively. Theoretical analysis shows that this particular type of coupling also excites the degenerate E11νmode, and this accounts, at least partially, for the measured variation in the parameters of the material. An alternative type of coupling, through small slots cut in the curved sides of the cavity, is described, and this should give better discrimination against the E11νmode and lead to measurements which are less dependent on the sample thickness. Experiments are described which bear this out, and variations in the measurements using the new coupling arrangement show, for the same sample-thickness range, a spread in permittivity and tan δ of 0.2 and 12%, respectively. View full abstract»

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  • Oblique-incidence millimetre-wave plasma diagnostics

    Page(s): 1035 - 1044
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1143 KB)  

    A beam of millimetre-wave radiation entering a plasma obliquely may re-emerge by refraction just as radio waves are returned to Earth by the ionosphere. The separation D between the points of entry and re-emergence depends on the angle of incidence ¿i, and on the electron-density distribution in the plasma. If D is studied as a function of ¿i, the electron-density distribution can be deduced by a method which is explained in the paper. The method is based on ray theory, and the validity of ray theory in this special application is studied in some detail. It is assumed throughout that the plasma is (a) cold, (b) isotropic and (c) collision-free The method has been tested experimentally, and an example of an electron-density profile obtained by it is given. View full abstract»

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  • Field decomposition in compressible magnetoplasmas by a perturbation technique

    Page(s): 1045 - 1047
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (384 KB)  

    The paper presents a method for the determination of the electromagnetic and pressure fields produced by a given distribution of source currents in a lossy, anisotropic, compressible plasma. With appropriate series expansions of the permittivity and compressivity tensors, a perturbation approach is used to decompose the coupled fields into partial fields which satisfy a family of recursive equations containing no tensor operators. The recursive equations are uncoupled, nonhomogeneous Helmholtz equations, similar to those governing an isotropic and compressible medium. The effective source-current density for the nth-order partial fields depends upon the interaction of the n ¿ 1 lower-order partial fields with the externally applied magnetic field. View full abstract»

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  • First-order nonlinear effects in travelling-wave tubes

    Page(s): 1048 - 1050
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (353 KB)  

    Previous analytical work on travelling-wave-tube (t.w.t.) nonlinear effects has been extended to include the effects of electron space-charge and nonzero beam-coupling impedance. Modulation transfer effects for single- and double-signal operation in a weakly saturated state are discussed and shown to be determined by the design parameters of the t.w.t. Large coupling impedance and low circuit loss are shown to reduce intermodulation signal power and crossmodulation effects. View full abstract»

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  • Zero-transient switching of a subharmonic parametric oscillator

    Page(s): 1051 - 1055
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (557 KB)  

    An analytical technique is presented for the determination of the time variation of the current necessary to switch phases of a subharmonic parametric oscillator within one cycle of the output voltage and with zero transient. An approximation to the required switching current is generated by a suitable shaping circuit, and the validity of the analysis is confirmed by practical observation. Using such switching techniques, the oscillator, which uses the diffusion capacitance of a junction diode, might be used to represent the binary variable and might have faster switching times than existing parametric computing elements. View full abstract»

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  • Frequency doublers using charge-storage/step-recovery diodes

    Page(s): 1057 - 1062
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    Computed results are given for the efficiency and power output of a p-n junction-diode frequency doubler operating in the charge-storage/step-recovery mode. These results are compared to those obtained with the same diode used as a nominally or overdriven varactor, and the limitations and advantages of the storage/recovery mode are discussed. It is shown that for moderate efficiencies, e.g. ¿3dB, the storage/recovery mode gives the best power output. For high efficiencies (better than ¿1dB), this mode can give excellent results if the forward-bias (contact) resistance is less than the reverse-bias series resistance. The results are verified with a high-frequency stripline doubler. View full abstract»

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  • Filter synthesis using Legendre polynomials

    Page(s): 1063 - 1064
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    Freely Available from IEEE
  • Distributed amplifiers: survey of the effects of lumped-transmission-line design on performance

    Page(s): 1065 - 1074
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    A survey of the effects of lumped-transmission-line design on the performance of distributed amplifiers is presented. A general formula for the gain of a distributed amplifier using nonuniform lines, but with image-impedance match at each connection, is given. The general formula for gain reduces to all the special formulas derived in the literature under assumed constraints in the network structure, and these results are tabulated. In order to make the paper more useful to research workers, an extensive bibliography of contributions related to distributed amplification is included. View full abstract»

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  • Universal winding for electrical-machine research

    Page(s): 1077 - 1083
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1043 KB)  

    Since the emergence of pole-amplitude modulation as a new winding logic, which has now been shown to be applicable both to single-speed and to change-speed machines, interest in the theory of electrical-machine windings has been increased. To enable the student and the research worker to gain an insight into the subject by direct experimentation, at a moderate cost and with an enormous saving of time, a universal winding has been devised, which is capable of simulating the windings of an unlimited number of actual machines. Various embodiments and examples of this versatile winding are described in the paper. View full abstract»

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  • Brushless and self-excited single-phase alternator

    Page(s): 1089 - 1095
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (866 KB)  

    The paper describes a brushless, self-excited alternator in which the reverse-rotation component of the armature m.m.f. is used to increase the excitation current as the load is increased. The excitation scheme is power-factor sensitive, since the increase is greater as the load becomes more inductive, and the voltage regulation is within that normally required from single-phase self-excited machines. An analysis is presented in which the nonlinearities essential for stable operation are discussed, and close agreement between predicted and measured load characteristics is obtained. View full abstract»

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  • Aircraft a.c. electrical systems using changeover contactors and rapid fault clearance

    Page(s): 1099 - 1104
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (873 KB)  

    Conventional aircraft electrical systems are liable to interruptions or disturbances for up to several seconds under fault conditions. Such interruptions may be limited to substantially less than 100ms by the use of a very simple nonparalleled system employing changeover contactors and forms of undervoltage and overvoltage protection which do not depend on time delays to discriminate between real faults and switching transients. The overvoltage protection acts rapidly enough to prevent the voltage rising to destructive levels in the event of, say, a regulator fault. In its simplest form, with two generators or with four generators arranged in two subsystems, the total generator capacity must be twice the maximum load, to ensure, that the failure of one generator will not result in loss of load, in the 2-generator case, this can be reduced to four thirds if the load can be divided into three equal parts, one of which may be discarded in the event of a generator failure. In the 4-generator case, the factor may be four thirds, with no loss of load with one generator failure if it is possible to divide the load into six equal parts. View full abstract»

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  • Discussion on ¿Barn hay drying¿

    Page(s): 1105 - 1106
    Save to Project icon | PDF file iconPDF (363 KB)  
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  • Turbogenerator end-region magnetic fields

    Page(s): 1107 - 1114
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    A simple qualitative method of estimating the radial and axial magnetic-field components in the end region of turbogenerators is described. The method, which utilises conducting paper, has been applied to two machines having outputs of 2.5 MW and 500 MW, and has given reasonable agreement with measured results obtained by means of search coils. Although the method is generally used for estimating the axial and radial components of the end-region magnetic field only, sufficient information can be obtained to enable the effect of general design changes to be predicted. View full abstract»

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  • Digital-computer methods in dynamic-response analyses of turbogenerator units

    Page(s): 1115 - 1130
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1564 KB)  

    A mathematical model for a turbogenerator unit is presented, based on the direct- and quadrature-axis equations of the generator, and associated equations for the prime mover and governor, and for the excitation control system. The solution of the equations of the complete model by digital computer is developed. In the representation of the generator, a method is explained by which the effective inductance coefficients and time constants in the direct and quadrature operational equations may be related to, and varied in accordance with, the magnetic conditions computed at each step advance in solution, thereby accounting for the effect of the generator magnetic-circuit characteristics on its transient response. The eddy-current paths in the solid rotor are first represented by an equivalent short-circuited winding in each axis, the subtransient parameters of which are those derived from short-circuit tests in the ordinary way. An improved rotor representation is then developed from a solution of the field equations for a simplified rotor model having a rectangular section and smooth surface. Beginning with the case of a large depth of flux penetration in the rotor body, corresponding to low-frequency rotor excitation, an equivalent-circuit interpretation of the solution of the field equations is formed, the low-frequency circuit parameters of which are then modulated at each integration step throughout solution to take account of different and higher incremental rates of magnetisation. A further method of computing the effects of rotor eddy currents is given in which the eddy-current paths are represented by ladder networks in each axis. The validity of the methods developed is examined by comparing computed results with those obtained from full-scale site tests on a 30 MW unit and on a 120 MW unit, for transient conditions provoked by load rejection, 3-phase short circuit and excitation reduction leading to pole slipping and rotor overvoltages. View full abstract»

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  • Power-system model

    Page(s): 1131 - 1138
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    The Central Electricity Generating Board is applying automatic control to some of the main functions of the Grid control centres and the generating stations. To facilitate part of this work a power-system analogue has been constructed. This is basically a 50c/s a.c. network with a unique simulation of generators and loads. A generator is simulated by a variable-frequency voltage behind a fixed reactance, and governor simulation is included, so that load excess or deficit will cause a change in system frequency. A load is represented by a voltage behind a resistance, the in-phase and quadrature components being separately varied to control the active and reactive power absorbed. View full abstract»

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  • Developments in power-system control

    Page(s): 1139 - 1148
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    Recent developments in system control by the CEGB, including the use of digital computers, are described in the paper. The CEGB 2-tier control system is being reinforced by `district¿ control rooms and new `area¿ control rooms at the existing area control centres, and by a new national control centre in London with selective electronic display. The changeover to 3-tier operation with district, area and national controls will be completed in 1968¿69. View full abstract»

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  • Some relay quantities for pilot-wire protection

    Page(s): 1149 - 1155
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (923 KB)  

    A reappraisal is made of multiterminal private pilot-wire protection. Pilot-wire relay operating and bias quantities are analysed separately. Possibilities of compensation to make relay quantities completely independent of pilot-wire characteristics for a multiterminal protection are examined for both circulating-current and opposed-voltage schemes. Practical methods of achieving such compensation are outlined. Discriminating margins for multiterminal protections are considered, and a basis for optimising the design of a 4-wire multiterminal private-wire protection is set out. An assessment is made of alternative schemes. 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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