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1887

Proceedings of the Institution of Electrical Engineers

Volume 124, Issue 8, August 1977

Volumes & issues:

Volume 124, Issue 8

August 1977

Design of minimum-phase finite-impulse-response digital filters
  • Author(s): J.H. Gilchrist
  • Source: Proceedings of the Institution of Electrical Engineers, Volume 124, Issue 8, p. 665 –668
  • DOI:  10.1049/piee.1977.0144
  • Type: Article
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  • p. 665 –668 (4)
    A method is presented which can be used for the direct design of minimum-phase finite-impulse-response digital filters with arbitrary prescribed modulus-squared characteristics. This method uses the Fletcher-Powell optimisation technique to minimise an L2p norm to obtain a nonnegative polynomial fit to the desired characteristics in a transformed domain. The coefficients of the filter are then obtained from the zeros of this polynomial. Examples of lowpass and bandpass filter designs are given using an L20 norm. A comparison of the passband and stopband ripples and their ratio is made with linear-phase filter designs.
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Cathode-ray-tube actuator in a noncontact analogue tachometer
  • Author(s): B.E. Jones  and  H.M. McNaughton
  • Source: Proceedings of the Institution of Electrical Engineers, Volume 124, Issue 8, p. 669 –672
  • DOI:  10.1049/piee.1977.0145
  • Type: Article
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  • p. 669 –672 (4)
    The paper describes an electro-optical method for noncontact measurement of instantaneous angular velocity of a shaft. The tachometer employs a standard cathode-ray tube as a voltage to light-spot position actuator, a black-white contrast edge on a diameter of the shaft end, and a photomultiplier light detector. The light spot is projected onto the shaft end and switched rapidly along the contrast edge about the shaft centre. Any detector output (at the switching frequency) is amplified, and by using a sampling function circle generator, the system is able to position the light-spot so as to minimise the detector output. Thus, this closed-loop system operates to maintain the light-spot on the contrast edge and the input to the circle generator is the tachometer output. The instrument must be focused on the shaft end; no special calibration is required and the light spot readily locks onto a rotating contrast edge. An experimental instrument has been used on shafts down to 3 mm in diameter, which has a range of at least 20000 rev/min in either direction, a bandwidth of about 1 kHz with a resolution of about 400rev/min limited by noise, owing to the effect of background light on the photomultiplier. Greater resolution may be obtained at the expense of bandwidth.
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Improved low-height antifading medium-wave antenna
  • Author(s): W.S. Davies
  • Source: Proceedings of the Institution of Electrical Engineers, Volume 124, Issue 8, p. 673 –680
  • DOI:  10.1049/piee.1977.0146
  • Type: Article
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  • p. 673 –680 (8)
    A new type of antifading broadcast antenna, consisting of typically four base-excited sloping wires located symmetrically about a central insulated support mast, offers significant advantages over conventional loaded antifading radiators. These advantages include a higher loop radiation resistance for mast heights below approximately 0.4λ, less inductive loading, and multiple parallel earthing points that are expected to reduce the earth losses when the soil is of low conductivity. The radiation resistances and associated antifading radiation patterns have been computed using two techniques; one with assumed sinusoidal-current distributions on the sloping wires and assumed negligible induced mast currents. The other involved a moment method analysis employing subsectional bases for the wire and mast currents. Results given by the first method agree well with both measurements performed on models having a nonmetallic mast, and the predictions given by the second method for masts having three or four insulated sections. If only two insulated mast sections are employed the induced mast current lowers the radiation resistance significantly; whereas, with a single continuous conducting mast section, the radiation pattern loses the required antifading form. It is considered that the new antenna will lower the minimum practical height of antifading radiators from the present value of approximately 0.35λ for conventional loaded monopoles to somewhere in the range 0.25λ to 0.3λ.
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Erratum: Reappraisal of computer-corrected network analyser design and calibration
Dynamic-stability analysis of synchronous machines including damper circuits, automatic voltage regulator and governor
  • Author(s): J.M. Stephenson  and  A.H.M.S. Ula
  • Source: Proceedings of the Institution of Electrical Engineers, Volume 124, Issue 8, p. 681 –688
  • DOI:  10.1049/piee.1977.0148
  • Type: Article
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  • p. 681 –688 (8)
    An improved method is presented for the study of the dynamic stability of synchronous generating sets. The complete d- and q-axis machine equations with a.v.r. and governor control loops, linearised for perturbations about a steady-state operating condition, are solved to give the natural frequencies and degree of stability of the various oscillating modes for a single machine connected to an infinite busbar. A 30 MW alternator with multiloop a.v.r. an governor is used to illustrate the use of the method for the study of rotor oscillations and the dynamic-stability limits. The effects of some principal parameters, including those of the machine damper circuits, are examined and important limitations in the accuracy of previous methods of analysis are demonstrated.
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Analytical method for estimating electromagnetic damping in a multistator stepping motor
  • Author(s): I.E.D. Pickup  and  D. Tipping
  • Source: Proceedings of the Institution of Electrical Engineers, Volume 124, Issue 8, p. 689 –696
  • DOI:  10.1049/piee.1977.0149
  • Type: Article
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  • p. 689 –696 (8)
    An analytical method is developed for predicting the electromagnetic damping of the single-step response of a multistator, variable-reluctance stepping motor operating with multiphase excitation. The analysis, which is based on the essentially sinusoidal variation of the time dependent quantities, takes into account the inherent magnetic nonlinearity. The prediction is made from relatively straightforward static tests at the machine terminals. The analytical results are compared with those obtained from experiment, and from numerical solution of the nonlinear differential equations, for a 5-phase multistator motor.
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Characterisation of a new machine with ferrite magnets by resolving the partial differential equation for the magnetic field
  • Author(s): M. Lajoie-Mazenc ; R. Carlson ; J. Hector ; J.J. Pesque
  • Source: Proceedings of the Institution of Electrical Engineers, Volume 124, Issue 8, p. 697 –701
  • DOI:  10.1049/piee.1977.0150
  • Type: Article
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  • p. 697 –701 (5)
    Studying a new ferrite magnet machine using electronic commutation, the authors have sought a method to determine the variation of the inductances and torque with the relative rotor/stator position. The method adopted uses the direct resolution of the finite difference equation of the potential vector. Subsequently it is shown how the properties and characteristic variables of the machine can be deduced from the numerical solution of the equation. Finally the results obtained are compared with those obtained experimentally.
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Damping and synchronising torques contributed by a voltage regulator to a synchronous generator: a quantitative assessment
  • Author(s): D.P. Sen Gupta ; N.G. Narahari ; J.W. Lynn
  • Source: Proceedings of the Institution of Electrical Engineers, Volume 124, Issue 8, p. 702 –708
  • DOI:  10.1049/piee.1977.0151
  • Type: Article
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  • p. 702 –708 (7)
    In the paper, the total damping and synchronising torques, which determine the dynamic stability of a synchronous generator in a power system, have been traced to their origin. The positive and negative components released or consumed by the voltage regulator, and by the various windings of the machine, have been isolated, with the object of making a quantitative assessment of the effects of various gains and time constants on the dynamic stability of a synchronous machine under different operating conditions. The analysis is based on the properties of quadratic invariance in tensor calculus. An alternative solution by network analysis has also been provided to establish the validity of the tensor approach.
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Wide-range high-performance time-ratio current control
General-purpose model of power-system loads
  • Author(s): G. Shackshaft ; O.C. Symons ; J.G. Hadwick
  • Source: Proceedings of the Institution of Electrical Engineers, Volume 124, Issue 8, p. 715 –723
  • DOI:  10.1049/piee.1977.0153
  • Type: Article
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  • p. 715 –723 (9)
    The paper is concerned with the derivation of a load model for use in studies of power-system dynamics and with he parameters to be used in such a model. It describes some system tests in which small voltage disturbances were imposed on a power-station auxiliary system and on consumer loads. The objectives of the tests were to determine the important factors in the power/voltage response of loads and to explore the possibility of determining the load composition and characteristics from such tests. The parameters obtained from the analysis of the small-disturbance tests on the power-station auxiliary system are used in an attempt to simulate a large disturbance to that system.
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Erratum: On-site investigation of electrohydraulic governors for water turbines
Erratum: Review of trends of large hydroelectric generating equipment
Control of a large linear system through system subdivision
Design of proportional-plus-derivative output feedback for pole assignment
  • Author(s): H. Seraji  and  M. Tarokh
  • Source: Proceedings of the Institution of Electrical Engineers, Volume 124, Issue 8, p. 729 –732
  • DOI:  10.1049/piee.1977.0157
  • Type: Article
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  • p. 729 –732 (4)
    The paper studies the problem of pole assignment in linear multivariable systems using proportional-plus-derivative output feedback. A simple expression is obtained for the closed loop characteristic polynomial in terms of the unity-rank proportional and derivative feedback matrices. It is shown that when the system order does not exceed twice the number of inputs or outputs, all system poles can be assigned arbitrarily, and the required feedback matrices are obtained from linear equations. When the system order exceeds this value, the pole assignment problem becomes nonlinear and may be solved using the available numerical methods. Examples are given for illustration.
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Discrete stochastic control with input constraints
Use of pole-shifting technique for improving power-system transient-stability regions
Erratum: Mutual capacitance between coplanar strips between earthed planes

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