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Volume 125
Issue 2
Proceedings of the Institution of Electrical Engineers
Volume 125, Issue 2, February 1978
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Volume 126 (1979)

Volume 125 (1978)

Volume 124 (1977)

Volume 123 (1976)

Volume 122 (1975)

Volume 121 (1974)

Volume 120 (1973)

Volume 119 (1972)

Volume 118 (1971)

Volume 117 (1970)

Volume 116 (1969)

Volume 115 (1968)

Volume 114 (1967)

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Volume 112 (1965)

Volume 111 (1964)

Volume 110 (1963)
Volume 125, Issue 2
February 1978
Investigation of attenuation by rainfall at 60 GHz
 Author(s): R.J. Humpleman and P.A. Watson
 Source: Proceedings of the Institution of Electrical Engineers, Volume 125, Issue 2, p. 85 –91
 DOI: 10.1049/piee.1978.0025
 Type: Article
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Attenuation at 60 GHz is investigated on a 680 m vertically polarised link, with two fastresponse raingauges and a dystrometer. Variations in attenuation for a given ground rainfall intensity are seen to be caused by dropsize variations. This conclusion is reached after conversion of point rainfall rates to path rainfall rates using a synthetic storm model, when the resultant variation of attenuation with path rainfall rate is seen to follow relationships predicted from the dystrometer. Nevertheless, on the average, the Laws/Parsons dropsize distribution is seen to be remarkably good for predicting attenuation from ground rainfall rates. Fading for one year was in excess of 15 dB for 10^{−3}% of the time. By inference, radio paths of 2 to 3km should thus be possible at 60GHz in the UK.
Rapid estimation of spectra from irregularly sampled records
 Author(s): J.B. Roberts and M. Gaster
 Source: Proceedings of the Institution of Electrical Engineers, Volume 125, Issue 2, p. 92 –96
 DOI: 10.1049/piee.1978.0026
 Type: Article
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p.
92
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Records of physical quantities often arise as continuous electrical signals. Spectral estimates may be formed either by analogue means or from digitised samples that are then processed on a computer, When the samples are provided at regularly spaced time instants, this can be achieved very quickly with the aid of the f.f.t (fast Fourier transform) algorithm. There are situations, however, where the data is known only at random time instants, and the paper is concerned with the computation of spectral estimates from such data. When the sample times are Poisson distributed, it has been shown, in previous papers, that unbiased aliasfree estimates can be formed, either through the correlation function or by a direct Fourier transform of short blocks of data. Random sampling introduces additional variability in these spectral estimates, and it is consequently necessary to process a large amount of data in order to achieve stable results. Unfortunately, this is very time consuming, most of the computer effort being spent evaluating sine and cosine functions which are then multiplied by the data samples. Here, two methods that can be used to simplify this operation are discussed. It is shown that when the sine and cosine functions are replaced by their equivalent rectangular waveforms, the resulting estimates can be related to spectral estimates through the Fourier expansion for the rectangular waves. A second way of speeding up the processing of Gaussian signals can be achieved by quantising the data to a sign bit and using the ‘arcsine’ rule to transform the autocorrelation function to that of the full signal. It is shown that when both techniques are used together, and the processing reduced to 1bit logical operations, valid spectral estimates can indeed be formed. These ideas are tested on various simulated sets of data.
An efficient minimumdistance decoding algorithm for convolutional errorcorrecting codes
 Author(s): W.H. Ng and R.M.F. Goodman
 Source: Proceedings of the Institution of Electrical Engineers, Volume 125, Issue 2, p. 97 –103
 DOI: 10.1049/piee.1978.0027
 Type: Article
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97
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Minimumdistance decoding of convolutional codes has generally been considered impractical for other than relatively short constraint length codes, because of the exponential growth in complexity with increasing constraint length. The minimumdistance decoding algorithm proposed in the paper, however, uses a sequential decoding approach to avoid an exponential growth in complexity with increasing constraint length, and also utilises the distance and structural properties of convolutional codes to considerably reduce the amount of tree searching needed to find the minimumdistance path. In this way the algorithm achieves a complexity that does not grow exponentially with increasing constraint length, and is efficient for both long and short constraint length codes. The algorithm consists of two main processes. Firstly, a directmapping scheme, which automatically finds the minimumdistance path in a single mapping operation, is used to eliminate the need for all short backup tree searches. Secondly, when a longer backup search is required, an efficient treesearching scheme is used to minimise the required search effort. The paper describes the complete algorithm and its theoretical basis, and examples of its operation are given.
Improvement on VarshamovGilbert lower bound on minimum Hamming distance of linear codes
 Author(s): A. Hashim
 Source: Proceedings of the Institution of Electrical Engineers, Volume 125, Issue 2, p. 104 –106
 DOI: 10.1049/piee.1978.0028
 Type: Article
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p.
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An improvement on the VarshamovGilbert lower bound on the minimum Hamming distance d of linear block codes is proposed. The improved bound is based on the assumption that, for an (n, k) block code, the number of distinct vectors resulting from the linear combination of every (d−2) columns of the paritycheck matrix is much less than the total number of vectors generated from such linear combinations. An expression for the largest possible number of distinct vectors obtainable for any (n, k) group code can therefore be introduced and shown to be a function of the weight distribution of the code.
Relationship between modal matrix and state transformation matrices for 2elementkind networks
 Author(s): K.V.V. Murthy and R.E. Bedford
 Source: Proceedings of the Institution of Electrical Engineers, Volume 125, Issue 2, p. 107 –108
 DOI: 10.1049/piee.1978.0029
 Type: Article
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p.
107
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Erratum: Lowfrequency correlator using a bucketbrigade analogue delay line
 Author(s): P.C. Fannin
 Source: Proceedings of the Institution of Electrical Engineers, Volume 125, Issue 2, page: 108 –108
 DOI: 10.1049/piee.1978.0030
 Type: Article
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p.
108
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Fully controlled regenerative bridges with halfcontrolled characteristics
 Author(s): W. Farrer and D.F. Andrew
 Source: Proceedings of the Institution of Electrical Engineers, Volume 125, Issue 2, p. 109 –112
 DOI: 10.1049/piee.1978.0031
 Type: Article
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The paper describes a means of control for fully controlled thyristor bridges which effects regeneration of energy to the a.c. supply source and still maintains the better powerfactor and ripple characteristics usually associated with halfcontrolled rectifier arrangements. The technique is applicable to polyphase bridge circuits but the advantages are greatest in the handling of large singlephase powers such as occur in a.c.fed traction systems. Although these advantages are applicable to d.c. motor control schemes the convertor bridge characteristics are naturally suited for use with currentsourcetype invertorcontrolled a.c. motors. Such control techniques may thus prove vital in the consideration of a.c.motor schemes for a.c.supplied traction applications.
Variablespeed inverterfed synchronous motor employing natural commutation
 Author(s): A.C. Williamson ; N.A.H. Issa ; A.R.A.M. Makky
 Source: Proceedings of the Institution of Electrical Engineers, Volume 125, Issue 2, p. 113 –120
 DOI: 10.1049/piee.1978.0032
 Type: Article
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A drive system is described which uses two conventional thyristor convertors to provide a d.c. link between a.c. mains and the varyingfrequency voltages of a synchronousmachine stator, both convertors being naturally commutated by line voltages; the result is a variablespeed drive. The paper describes a detailed analysis of machine behaviour in the absence of saturation, but taking account of winding resistances. This analysis is used to investigate the effects of assumptions made in deriving a simple analysis, which takes account of magnetic saturation. The validity of the simple analysis is demonstrated by comparison with results obtained from tests on a practical drive system.
Slewregion instability of permanentmagnet stepmotors
 Author(s): A.J.C. Bakhuizen and J.H. Wouterse
 Source: Proceedings of the Institution of Electrical Engineers, Volume 125, Issue 2, p. 121 –124
 DOI: 10.1049/piee.1978.0033
 Type: Article
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p.
121
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In treating the phenomenon of the slewregion instability of the permanent magnet stepmotor the authors are aware of its strong relation to the problem of hunting in synchronous machines. The latter problem was treated by Rogowski and many others from 1915 onwards but the authors believe that their approach leads to a more detailed understanding of the phenomenon of spontaneous vibrations, as well as the fact that the results are obtained by way of simple and straightforward mathematics.
Sensed reconnection of inductionmotor supplies
 Author(s): B. Thomason ; P.J. Gallagher ; W. Shepherd
 Source: Proceedings of the Institution of Electrical Engineers, Volume 125, Issue 2, p. 125 –128
 DOI: 10.1049/piee.1978.0034
 Type: Article
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p.
125
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The paper indicates how the reconnection of the supply to a running induction motor can be effected in a manner that avoids excessive transient disturbances. An optimum condition is postulated for a matched reconnection and the paper indicates how this selected reclosure can be brought about. Typical results obtained by the sensedswitching technique are illustrated for a 3.75 kW (Shp) motor and are compared with results obtained during random switching of the same machine.
The modern transient network analyser and its role in analysis and design of electrical systems
 Author(s): W.M. Ritchie and J.T. Pender
 Source: Proceedings of the Institution of Electrical Engineers, Volume 125, Issue 2, p. 129 –134
 DOI: 10.1049/piee.1978.0035
 Type: Article
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p.
129
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The complementary functions of the transient network analyser and the digital computer are examined and further consideration is given to the most appropriate spheres of application of the analyser. A description is given of the design of a new versatile solidstate analyser and its use in a specific investigation of overvoltages due to transmissionline energisation.
Transient security assessment methods
 Author(s): H. Rudnick and A. Brameller
 Source: Proceedings of the Institution of Electrical Engineers, Volume 125, Issue 2, p. 135 –140
 DOI: 10.1049/piee.1978.0036
 Type: Article
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p.
135
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The paper provides a comparative study of three methods for transient security assessment of power systems: stepbystep simulation, Lyapunov's direct method and an empirical method based on the kinetic energy of the system. Different ways of formulating the Lyapunov algorithm are shown, and the basic concepts are summarised in a simple form. Particular emphasis is given to the application of the methods to relatively large practical problems with case studies and comparative results provided.
Convertor control with selective reduction of line harmonics
 Author(s): K.A. Krishnamurthy ; G.K. Dubey ; G.N. Revankar
 Source: Proceedings of the Institution of Electrical Engineers, Volume 125, Issue 2, p. 141 –145
 DOI: 10.1049/piee.1978.0037
 Type: Article
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p.
141
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In the paper, a new method of controlling the power of a d.c. series motor drive using the forcedcommutation principle is proposed and investigated. In this method, it is possible to reduce any one unwanted harmonic and its multiples to a low value. However, only the reduction of triplen harmonics is investigated in the paper. A power circuit to realise the proposed method is also suggested. A slight modification of the proposed control circuit yields symmetrically pulsewidth modulated and sinusoidally modulated schemes with two chops per halfcycle. These two and the recently reported scheme using symmetrical pulsewidth modulation with a single chop per halfcycle are investigated and are compared with the proposed new method with regard to the line side harmonic components, power factor and the motor performance characteristics. Experimental verification of the basic principles involved is made. The experimental values closely agree with the theoretical results.
New power convertor technique employing power transistors
 Author(s): A.R. Daniels and D.T. Slattery
 Source: Proceedings of the Institution of Electrical Engineers, Volume 125, Issue 2, p. 146 –150
 DOI: 10.1049/piee.1978.0038
 Type: Article
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p.
146
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A new power convertor, using power transistors in a switching mode as the main power elements, has been introduced. This convertor is capable of conversion from a fixed 3phase source to variable frequency, controlled output current, such that the operating frequency range is not limited by the supply frequency. The power transformers, inductors and capacitors normally associated with many existing forms of such a convertor are no longer needed. Further advantages of the new convertor are that it is capable of accepting regenerative power, operates without the need for a d.c. link and the input displacement factor is unity, regardless of the output condition.A new mode of operation, that of class ABD, has been introduced, which allows the switching rate of the power transistors to be considerably reduced for a given output. Such a technique reduces switching losses and results in a much less severe operational environment for the power transistors. It also helps to improve the power factor to a value close to unity.The present paper describes a 3phase to singlephase convertor but the method can be used to provide a fullyregenerative 3phase to 3phase static converter, using only 18 power elements and producing a variable frequency, 3phase controlled output current whose waveform is a very close approximation to a sinusoid.
Distribution system voltage studies using simulation techniques
 Author(s): E. Economakos
 Source: Proceedings of the Institution of Electrical Engineers, Volume 125, Issue 2, p. 151 –152
 DOI: 10.1049/piee.1978.0039
 Type: Article
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p.
151
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A problem very familiar to powerdistribution engineers, namely, the distribution systems voltage studies and regulation, is dealt with in this paper. Simulation techniques are used and models of the system and its loading are formed. The statistics of the load variations are considered and a practical way for using them is suggested. A method of checking the feasibility of any voltage regulation program is developed. If a program is feasible, an optimal area for the regulator operation is deter mined via an optimisation procedure.
Simple method of measuring active power in short time variations
 Author(s): E. Besag
 Source: Proceedings of the Institution of Electrical Engineers, Volume 125, Issue 2, page: 152 –152
 DOI: 10.1049/piee.1978.0040
 Type: Article
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p.
152
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Simple method of measuring active power in short time variations
 Author(s): I. Peled
 Source: Proceedings of the Institution of Electrical Engineers, Volume 125, Issue 2, page: 152 –152
 DOI: 10.1049/piee.1978.0041
 Type: Article
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p.
152
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Performance and stability of a magnetic suspension device using a tuned LCR circuit
 Author(s): S. Hagihara
 Source: Proceedings of the Institution of Electrical Engineers, Volume 125, Issue 2, p. 153 –156
 DOI: 10.1049/piee.1978.0042
 Type: Article
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p.
153
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This paper presents an analysis of a magnetic suspension device utiising a tuned LCR circuit. The leakage flux of the electromagnet is taken into account. The method of averaging is applied to nonlinear differential equations which describe the system under the assumption that the system is operating near an equilibrium state. Response characteristics, i.e. the gap distance in an equilibrium state and the equivalent spring constant, are theoretically obtained. The static and dynamic stability criteria are sought. It is demonstrated that a quasiperiodic oscillation occurs in a system which is dynamically unstable. in this case the suspended object oscillates periodically in the steady state. The analytical result is confirmed by experimental observation.
Speech output from a computercontrolled watersupply network
 Author(s): F. Fallside and S.J. Young
 Source: Proceedings of the Institution of Electrical Engineers, Volume 125, Issue 2, p. 157 –161
 DOI: 10.1049/piee.1978.0043
 Type: Article
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p.
157
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A system is described which provides for the output of information from a real engineering database in spoken form. Data extracted from the database is converted by the system, using its own predefined knowledge of the information domain and a knowledge of simple English, into a sequence of words and an associated pitch contour. The spoken output is then generated by the concatenation and resynthesis of previously analysed stored isolated words using a hardware digital speech synthesiser.
Influence of superimposed direct voltage on the a.c. dielectric properties of some dielectrics
 Author(s): M. Rapoš and J.H. Calderwood
 Source: Proceedings of the Institution of Electrical Engineers, Volume 125, Issue 2, p. 162 –164
 DOI: 10.1049/piee.1978.0044
 Type: Article
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p.
162
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Changes in the a.c. dielectric properties of inhomogeneous insulating materials in the presence of a superimposed direct voltage are analysed and explained on the basis of a model consisting of a simple sandwich capacitor, taking into account not only macroscopic dielectric properties, but also the behaviour of the charge carriers involved. The classical MaxwellWagner treatment is therefore modified to take account of a possible variation of chargecarrier density caused by superimposed direct voltage, with a consequent dependence of a.c. permittivity and dielectric loss on the superimposed direct voltage.
Influence of stress on rotational loss in silicon iron
 Author(s): A. Basak and A.J. Moses
 Source: Proceedings of the Institution of Electrical Engineers, Volume 125, Issue 2, p. 165 –168
 DOI: 10.1049/piee.1978.0045
 Type: Article
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p.
165
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The stress sensitivity of rotationalpower loss in silicon iron has been investigated. The loss increases with tensile stress applied parallel to the rolling direction and decreases with compression. The opposite occurs when the stress is applied perpendicular to the rolling direction. The loss varies in a similar fashion over the fluxdensity range investigated. Increasing the frequency causes the loss to rise drastically and also increases its stress sensitivity. It has also been shown theoretically that the angle of lag of the flux density behind the applied field increases with stress and varies during the magnetising cycle.
Experience at Edmonton (GLC) of generating electricity using refuse as fuel
 Author(s): F.T.F. Wiggin
 Source: Proceedings of the Institution of Electrical Engineers, Volume 125, Issue 2, p. 169 –172
 DOI: 10.1049/piee.1978.0046
 Type: Article
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p.
169
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The paper describes a continuous powergeneration process incinerating untreated domestic/industrial refuse mix as a sole fuel for electricity production based on conventional powerstation practise. Details of the background, design and expected performance of the plant, as commissioned, are given. Problems of initial operations included difficulties with specialised refuse and residuals, handling equipment, as well as catastrophic failures of boiler tubes from flue side corrosion/erosion within an average 4000 operating hours for individual incinerator/boiler heat exchangers. Explanations are provided, and details given, of remedial measures involving considerable modifications to equipment. The experience of final sustained successful operations until January 1975 is discussed, including the qualities and performance of refuse as sole fuel for steam generation. Operating and thermal efficiencies, relevant to energy conversion and stage processes, including ferrous metal recovery from residuals, are noted. Conclusions arrived at relate to successful commercial operations being achieved by attention to obtaining really efficient combustion and balancing the requirement for dealing with the heavy fluefouling characteristics of refuse burning against the effects of renewed corrosion/erosion on exposed or reexposed boilertube surfaces. The economics of overall operations and achievement of viable largescale electricity production with refuse disposal are reported.
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