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Volume 122
Issue 2
Proceedings of the Institution of Electrical Engineers
Volume 122, Issue 2, February 1975
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Volume 126 (1979)
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Volume 122, Issue 2
February 1975
Data transmission with variable-redundancy error control over a high-frequency channel
- Author(s): R.M.F. Goodman and P.G. Farrell
- Source: Proceedings of the Institution of Electrical Engineers, Volume 122, Issue 2, p. 113 –118
- DOI: 10.1049/piee.1975.0022
- Type: Article
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Results of computations and field tests on a binary-data-transmission system, operating at 1 kbaud over an h.f. channel, are presented. Error correction is effected by means of error detection and automatic request for repeat, via a feedback channel (a Post Office private line). A set of short, fixed-block-length cyclic codes is available, a code of appropriate redundancy being automatically selected to match the varying channel conditions. The decision about which code to use is made at the receiver, and the transmitter is informed via the feedback channel. The results show that relatively simple, reliable, and efficient data communication can be realised by this means.
Zero-crossing preservation in the low-bit-rate pseudorandomly dithered quantisation of speech signals
- Author(s): M. Chen and L.F. Turner
- Source: Proceedings of the Institution of Electrical Engineers, Volume 122, Issue 2, p. 119 –123
- DOI: 10.1049/piee.1975.0023
- Type: Article
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In earlier investigations, it has been found that, at low bit rates, the dithered quantisation of speech samples in pulse-code modulation (p.c.m.) is perceptually pleasing but is less intelligible than normal fixed-level quantised p.c.m. Also, it has been suggested that a possible cause of the reduced intelligibility of the dithered p.c.m. is the effect that the dithering has on the zero crossings of the speech signal. This paper reports on an investigation into this suggestion. A number of methods of dithered quantisation are considered in which the zero crossings of the speech signal are preserved, and the results of intelligibility tests carried out to compare the various methods of dithering are presented. The statistical analysis of the results shows that, for 3, 4 and 5 bits per sample quantisation, two of the methods of dithered quantisation are significantly more intelligible than normal, correspondingly low-bit-rate p.c.m., and the advantage is better than 1 bit per sample.
Two-dimensional computer analysis of a dielectric surface-loaded GaAs bulk element
- Author(s): S. Kataoka ; M. Morisue ; M. Kawashima
- Source: Proceedings of the Institution of Electrical Engineers, Volume 122, Issue 2, p. 124 –130
- DOI: 10.1049/piee.1975.0024
- Type: Article
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It is well established by experiment and theory that a travelling high-field domain in a GaAs bulk element is suppressed by surface loading of a dielectric material on the GaAs. To investigate this effect in more detail, a computer analysis based on a 2-dimensional model is performed. For the simulation, the full surface of a GaAs element of n = 5 × 1015cm−3, L = 8.7 μm and d = 4.2 μm is loaded with dielectric materials of various permittivities and 0.9 μm thick. The cathode and anode are extended to infinity, where a linear potential distribution is assumed. The results are summarised as follows:(a) Space charges in GaAs are accumulated near the boundary between GaAs and the dielectric material, and consequently the electric field from the space charges leaks into the dielectric material.(b) As a result, the growth of a high-field domain is suppressed, and no cyclic generation of the domain occurs, if the relative permittivity of the dielectric material is 500 or more.(c) A static voltage/current characteristic of the GaAs bulk element, loaded with a dielectric material of relative permittivity 10 000, shows a current saturation.(d) All results of the present computer simulation show a qualitative agreement with the reported experiments.
Geostationary-satellite earth coverage
- Author(s): G. Millington
- Source: Proceedings of the Institution of Electrical Engineers, Volume 122, Issue 2, p. 131 –134
- DOI: 10.1049/piee.1975.0025
- Type: Article
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The basic problem considered is the relation of the shape of the beam of a geostationary satellite antenna to the area that it covers on the surface of the earth. It is envisaged that circular or elliptical beams may be used, but the beam is defined in general terms by a beam contour on a beam plane perpendicular to the beam axis by two angular co-ordinates δ andψ, while the earth contour in which the beam cuts the surface of the earth is defined by the latitude θ and the longitude φ. Corresponding points on the two contours are linked by the direction cosines of the line from the satellite passing though them, leading to equations for finding θ and φ from δ and and ψ and vice-versa. The process of finding the shape of a beam to serve a specified area on the earth with as little excess coverage as possible is discussed, with the limited possibility of compensating for the difference in clear-air attenuation in different directions from the satellite. The major problem of absorption, for example, by rain or clouds, is regarded as outside the scope of the paper.
Modified butterworth functions with low Q factor
- Author(s): Khalil Massad and R. Yarlagadda
- Source: Proceedings of the Institution of Electrical Engineers, Volume 122, Issue 2, p. 135 –136
- DOI: 10.1049/piee.1975.0026
- Type: Article
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A method is given to determine the coefficients of a modified lowpass maximally flat (at the origin) Butterworth polynomial, with a reduced dominant-pole-pair Q factor at the expense of increasing order of the transfer function with multiplicity of the dominant pole pair greater than one.
Hardware implementation of a recursive digital filter for m.t.i. radar
- Author(s): A.R. Elliott ; S.S. Haykin ; C.D. Hawkes
- Source: Proceedings of the Institution of Electrical Engineers, Volume 122, Issue 2, p. 137 –141
- DOI: 10.1049/piee.1975.0027
- Type: Article
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The important features of the hardware implementation of a recursive digital filter for use with m.t.i. radar are described.The filter can operate with pulse widths of 0.8–6 μs, over a wide range of pulse-repetition frequencies, and can handle up to 512 range bins in multiples of 8. It is programmable to realise a 1st-, 2nd- or 3rd-order Butterworth or Chebyshev frequency response, by simply entering three appropriate binary coefficients into the system. Experimental results are included to verify the performance of the system.
Effect of numerical integration on the poles and zeros of a transfer function
- Author(s): C.A.G. Enstone
- Source: Proceedings of the Institution of Electrical Engineers, Volume 122, Issue 2, p. 142 –144
- DOI: 10.1049/piee.1975.0028
- Type: Article
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An expression for the transfer function of a numerical integrator is derived, and is illustrated by a mapping in the complex plane. Analysing a complete system using numerical integration is shown to be equivalent to displacing the poles and zeros of its transfer function. A simple graphical method for determining this displacement is described. The implicit Euler, trapezoidal and Shichman integration formulas are considered in detail. It is shown that these are special cases of a general formula, which possesses A stability. The trapezoidal formula is the most accurate A -stable equation, although it requires a reliable method of step-length adjustment. The implicit Euler and Shichman formulas sacrifice accuracy for better stability properties, when using large step lengths.
Unified theory of cascade synthesis
- Author(s): K. Imamura ; J.O. Scanlan ; J.D. Rhodes
- Source: Proceedings of the Institution of Electrical Engineers, Volume 122, Issue 2, page: 144 –144
- DOI: 10.1049/piee.1975.0029
- Type: Article
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Part symmetrisation of 3-phase windings
- Author(s): A.R.W. Broadway
- Source: Proceedings of the Institution of Electrical Engineers, Volume 122, Issue 2, p. 145 –148
- DOI: 10.1049/piee.1975.0030
- Type: Article
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Polyphase symmetrisation has become a valuable technique in the design of pole-amplitude-modulated (p.a.m.) windings. Electrical unbalance in asymmetrical windings has been almost completely eliminated by its application. Difficulties have remained only in a few, but very important, special cases, such as in p.a.m. machines with very small numbers of slots per pole per phase. Part symmetrisation is an extension of the basic symmetrising principle. It permits either the negative-sequence winding component, or the zero-sequence winding component, but not both, to be eliminated from a 3-phase winding. It has found application mainly for the elimination of the negative sequence winding component, since the zero sequence has little or no adverse effect in a winding connected in star. Many p.a.m. windings with a high zero-sequence content for one or other of the main pole numbers have been designed and are currently in use. One such winding, for 4/6 poles in 24 slots, is discussed in detail.
Axial magnetic forces in induction motors with skewed slots
- Author(s): V. Subrahmanyam
- Source: Proceedings of the Institution of Electrical Engineers, Volume 122, Issue 2, p. 149 –153
- DOI: 10.1049/piee.1975.0031
- Type: Article
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A comprehensive analysis of the axial force experienced by the rotor of an induction motor, as a function of slip, is presented. It is shown that the varying saturation along the stack of a skewed induction motor considerably affects the axial force due to skew. The calculated values obtained for the force are found to compare quite favourably with experimental results. It is also established that the force decreases with increase in the airgap length.
Pole-change windings for linear induction motors
- Author(s): J.F. Eastham and M.J. Balchin
- Source: Proceedings of the Institution of Electrical Engineers, Volume 122, Issue 2, p. 154 –160
- DOI: 10.1049/piee.1975.0032
- Type: Article
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Pole-change techniques are potentially valuable for the speed control of linear induction motors. However, they are more difficult to apply in the linear case because of the nonuniform nature of the airgap flux. This precludes the use of parallel paths which are normally employed to reduce the complexity of the switching. The paper describes a new winding connection technique, and shows how it can reduce the number of switch contacts required. The method requires the series connection of alternate coils to form one winding; the remaining coils form a second. Parallel connections are then made between these two windings. An analysis is presented that gives the currents in any general set of serially connected coil groups connected to independent voltage sources. From this, the complete electrical and mechanical performance of the machine can be calculated. The technique can deal with any asymmetric windings having parallel paths, and, while it is ideally suited to the machines under consideration, it has other potential applications. The work is supported by a selection of experimental results that were taken from a pole-change linear motor driving a disc secondary.
IEE Conference Publication 99. Electricity distribution: CIRED 1973. Part 2: Discussion
- Source: Proceedings of the Institution of Electrical Engineers, Volume 122, Issue 2, page: 160 –160
- DOI: 10.1049/piee.1975.0033
- Type: Article
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Transfer functions for variable-frequency induction motors with high-inertia loads
- Author(s): W. Charlton
- Source: Proceedings of the Institution of Electrical Engineers, Volume 122, Issue 2, p. 161 –162
- DOI: 10.1049/piee.1975.0034
- Type: Article
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A variable-speed induction motor is a nonlinear system, but, for small perturbations about an equilibrium point, it is approximately linear. For the case of “high”-inertia loads a simplified approximate transfer function is proposed that relates speed variations to input-frequency variations. A method of determining the “high” criterion is suggested and computed. Predicted and measured results are compared.
D.C. dynamic braking of induction motors with secondary capacitors
- Author(s): T.G. Bland and W. Shepherd
- Source: Proceedings of the Institution of Electrical Engineers, Volume 122, Issue 2, p. 163 –164
- DOI: 10.1049/piee.1975.0035
- Type: Article
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The presence of secondary-circuit capacitance permits large torque to be developed in induction motors at high speeds, with d.c. dynamic braking. Variation of braking torque at fixed speed can be achieved by variation of excitation current or capacitance, or by the inclusion of resistance in series or parallel with the capacitor. Test results are given for an experimental drive with a 3-phase wound-rotor machine. Computed performance curves, taking saturation of the machine into account, give acceptable agreement with the experimental results.
Induction-run performance of single-phase motors
- Author(s): O.I. Butler
- Source: Proceedings of the Institution of Electrical Engineers, Volume 122, Issue 2, p. 165 –167
- DOI: 10.1049/piee.1975.0036
- Type: Article
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On a basis of the “exact” equivalent circuit of a single-phase induction motor operating on its main winding only, accurate solutions are obtained for (a) speed and torque at pullout,(b) speed and torque-gradient at zero torque, and (c) torque, current, power factor and efficiency at any speed. These are derived for a gap m.m.f. sinusoidally distributed and modified in a simple manner for the presence of space harmonics.
Discussion on “Distance-protection comparator with signal-dependent phase-angle criterion”
- Source: Proceedings of the Institution of Electrical Engineers, Volume 122, Issue 2, p. 167 –168
- DOI: 10.1049/piee.1975.0037
- Type: Article
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Some concepts involved in the analysis of the magnetic field in cage induction machines
- Author(s): K.J. Binns and E. Schmid
- Source: Proceedings of the Institution of Electrical Engineers, Volume 122, Issue 2, p. 169 –175
- DOI: 10.1049/piee.1975.0038
- Type: Article
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The precise meaning of terms widely used in the analysis of harmonic fields in the airgaps of rotating machines is examined. The available methods of analysis of induction-motor fields are compared, and a simplified approach to field harmonics involving the concept of modulation is outlined. The flux components observed at stator and rotor in a cage-rotor machine are classified, and their relative significance in producing loss is examined by experiment. An unusual method of displaying the total flux spectrum is demonstrated, and this clearly shows that considerable simplification is possible by neglecting certain harmonics that, in the case of loss, are relatively unimportant.
IEE North Midland Centre: Chairman's address. The engineer in electricity distribution
- Author(s): H. Pickup
- Source: Proceedings of the Institution of Electrical Engineers, Volume 122, Issue 2, p. 175 –176
- DOI: 10.1049/piee.1975.0039
- Type: Article
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Solution of the transmission-line equations for lossy conductors and imperfect earth
- Author(s): Clayton R. Paul
- Source: Proceedings of the Institution of Electrical Engineers, Volume 122, Issue 2, p. 177 –182
- DOI: 10.1049/piee.1975.0040
- Type: Article
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A numerically stable and efficient method of diagonalising the product of the per-unit-length impedance and admittance matrices for multiconductor transmission lines with lossy conductors or lossy earth return is presented. Cases are discussed where, by an approximation, the product of these matrices, which is complex and frequency-dependent, can be diagonalised using a real, frequency-independent modal-decomposition matrix. Frequency dependence is included in the calculation of the modal-propagation constants.
IEE Conference Publication 123. Power electronics: semiconductors and their applications
- Source: Proceedings of the Institution of Electrical Engineers, Volume 122, Issue 2, page: 182 –182
- DOI: 10.1049/piee.1975.0041
- Type: Article
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Optimal profiles of disc-type spacers for gas insulation
- Author(s): T. Takuma and T. Watanabe
- Source: Proceedings of the Institution of Electrical Engineers, Volume 122, Issue 2, p. 183 –188
- DOI: 10.1049/piee.1975.0042
- Type: Article
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By adopting the suitable contact angle of a disc-type spacer, the surface flashover may be effectively suppressed on account of the decrease of the maximum field strength at the spacer surface. The calculation has clarified that the optimal contact angle of the spacer is 60–70° according to the relative permittivity of the spacer for R2/R1 (ratio of inner and outer electrode radii) = 1/3, and that 20–30% decrease in the maximum strength can be brought about in various spacer-electrode arrangements. The effect on the field-relaxation of R2R1, the relative permittivity of the spacer, and the spacer shape have been studied. Experiments in air at atmospheric pressure and in compressed SF6 have verified that very few flashovers take place at the surface of the field-relaxing spacers.
Speed and torque control of a single-phase linear induction motor
- Author(s): D.B. Watson
- Source: Proceedings of the Institution of Electrical Engineers, Volume 122, Issue 2, p. 188 –189
- DOI: 10.1049/piee.1975.0043
- Type: Article
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New technique for quadrilateral distance relay
- Author(s): A.T. Johns ; Y.G. Paithankar ; M.T. Sant ; V.T. Ingole
- Source: Proceedings of the Institution of Electrical Engineers, Volume 122, Issue 2, p. 189 –190
- DOI: 10.1049/piee.1975.0044
- Type: Article
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New superconducting switch: field-circuit version
- Author(s): R.V. Harrowell
- Source: Proceedings of the Institution of Electrical Engineers, Volume 122, Issue 2, p. 191 –192
- DOI: 10.1049/piee.1975.0045
- Type: Article
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Sufficient conditions for the nonoscillation of nonlinear pulse-controlled systems
- Author(s): C.J. Harris
- Source: Proceedings of the Institution of Electrical Engineers, Volume 122, Issue 2, p. 193 –196
- DOI: 10.1049/piee.1975.0046
- Type: Article
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In this paper, the sufficient conditions for the absence of periodic modes for unforced nonlinear pulse-controlled feedback systems are given. These criteria relate to the behaviour of discrete nonlinear feedback systems within the Popov-Hurwitz sector, and the structurally similar in form to the well known circle and Popov criteria of the frequency domain, with the same simple graphical interpretation. The pulse controllers under consideration are of the pulsewidth or pulse-amplitude type, and a general classification of pulse controllers is given. Illustrative examples of systems that fail the Aizerman and Kalman conjectures are investigated with the techniques developed in the paper to evaluate the largest nonlinearity sector that guarantees the absence of certain periodic modes.
Eigenvalue assignment in linear optimal-control systems via reduced-order models
- Author(s): S. Vittal rao and S.S. Lamba
- Source: Proceedings of the Institution of Electrical Engineers, Volume 122, Issue 2, p. 197 –201
- DOI: 10.1049/piee.1975.0047
- Type: Article
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Algorithms are currently available for the solution of certain types of optimal-eigenvalue-assignment problems in which the eigenvalues of a given system are required to be shifted into preassigned locations or region while also minimising an appropriate quadratic-performance criterion. All the known methods for a solution of the above problem are based on manipulation of the original nth-order system matrices even if only r eigenvalues (r ≥ n) of the original system are to be reassigned. On the contrary, the method proposed in this paper, for a solution of the above problem, employs an rth-order equivalent model, which leads to a solution via manipulation of rth-order matrices only. The method also ensures that the remaining n — r eigenvalues of the original system are not disturbed and are carried over to the resultant feedback system. It has been shown in the paper that the suggested procedure brings about a considerable saving in computation time, and also requires less computer storage. Two numerical examples have been included to illustrate the suggested technique.
Hierarchical optimisation of a water-supply network
- Author(s): F. Fallside and P.F. Perry
- Source: Proceedings of the Institution of Electrical Engineers, Volume 122, Issue 2, p. 202 –208
- DOI: 10.1049/piee.1975.0048
- Type: Article
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The paper presents the results of an investigation of the feasibility and implementation of an optimal online control to a water-supply network in the United Kingdom. The network, which has over 70 principal nodes, is reduced to an equivalent control problem with 6 state variables, which are the dominant reservoir heights, 10 control inputs, which are the major pump-station outputs, and 6 disturbances, which are the lumped zone consumptions. The control objective is the supply of water to the consumer over a 24 h period at minimum cost, subject to the 16 constraints on controls and states at each interval. To overcome the dimensionality problem associated with discrete-time optimal control the optimisation is carried out using a decomposition technique due to Lasdon and Tamura, which employs Lagrange duality theory. The paper describes the formulation of the network equations, the theory of the optimisation method, and gives typical results for the optimal operation of the system for typical weekday consumption. The results show a worthwhile cost saving over the control strategy in use during the study period, and computational experience indicates that the method is appropriate for optimal online control in a predictive environment.
Application of multivariable control theory to hydraulic models
- Author(s): D.J. Ball and G.C. Barney
- Source: Proceedings of the Institution of Electrical Engineers, Volume 122, Issue 2, p. 209 –212
- DOI: 10.1049/piee.1975.0049
- Type: Article
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Civil engineers have used scale models of rivers and estuaries for many years. The control of models with two interacting tide generators is particularly difficult, and has previously been implemented on a purely intuitive basis. This paper describes work carried out to identify accurately and control a model of the River Mersey. Multivariable theory was used to design the precompensating controller, which in use resulted in considerable improvements to the model performance.
Synthesis of a class of nonlinear systems in multidimensional frequency domain
- Author(s): Martin Schetzen ; V.S. Bansal ; O. Goyal
- Source: Proceedings of the Institution of Electrical Engineers, Volume 122, Issue 2, page: 212 –212
- DOI: 10.1049/piee.1975.0050
- Type: Article
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Calculation of the charge trajectories in a streaming dielectric liquid by means of a compound stream function
- Author(s): K. Asano and B. Makin
- Source: Proceedings of the Institution of Electrical Engineers, Volume 122, Issue 2, p. 213 –218
- DOI: 10.1049/piee.1975.0051
- Type: Article
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The exact calculation of a charge trajectory in a streaming dielectric liquid requires the solution of the coupled Maxwell and Navier-Stokes equations, which can be solved using lengthy iterative numerical techniques. A simple alternative method is proposed which gives an analytical solution for the particular case when the spacecharge density is small. The technique is applied to a cylindrical wire located centrally between two parallel plates with a transverse liquid flow. Electrical and hydrodynamic stream functions are derived separately and are combined to give the charge trajectories for several values of the electric and flow parameters. The results are considered for the application to high-voltage streaming generators.
Measurement of probability-distribution functions sensitive technique for the study of conduction phenomena in liquid dielectrics
- Author(s): Anand Khare
- Source: Proceedings of the Institution of Electrical Engineers, Volume 122, Issue 2, p. 219 –222
- DOI: 10.1049/piee.1975.0052
- Type: Article
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The paper outlines a technique for sensitive measurement of conduction phenomena in liquid dielectrics. The special features of this technique are the simplicity of the electrical system, the inexpensive instrumentation and the high accuracy. Detection, separation and analysis of a random function of current that is superimposed on the prebreakdown direct current forms the basis of this investigation. In this case, prebreakdown direct current is the output data of a test cell with large electrodes immersed in a liquid medium subjected to high direct voltages. Measurement of the probability-distribution function of a random fluctuating component of current provides a method that gives insight into the mechanism of conduction in a liquid medium subjected to high voltages and the processes that are responsible for the existence of the fluctuating component of the current.
Dielectric breakdown of polyethylene under gamma irradiation
- Author(s): Y. Kako and Y. Tsutsumi
- Source: Proceedings of the Institution of Electrical Engineers, Volume 122, Issue 2, p. 223 –224
- DOI: 10.1049/piee.1975.0053
- Type: Article
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The d.c. and impulse electric strengths of high-density polyethylene films, which were recessed and metallised on both sides to prevent external partial discharge, were measured with and without γ irradiation of intensity 1.4×104 r/h, in the temperature range from −196°C to 110°C. Radiation had little significant effect on the results.
Influence of an insulating film on the breakdown voltage of transformer oil in nonuniform fields
- Author(s): C.A. Evangelou ; A.A. Zaky ; I.Y. Megahed
- Source: Proceedings of the Institution of Electrical Engineers, Volume 122, Issue 2, p. 225 –226
- DOI: 10.1049/piee.1975.0054
- Type: Article
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The breakdown voltage of air-saturated transformer oil has been measured as a function of gap settings between a point and an aluminium-sphere electrode. By using a sufficient range of gap settings, it is shown that the presence of an electrolytically formed anodic oxide film on the spherical electrode markedly affects the polarity dependence of breakdown-voltage/gap-length characteristics.
IEE East Midland Centre: Chairman's address. Management of plant engineering operations
- Author(s): B. Thompson
- Source: Proceedings of the Institution of Electrical Engineers, Volume 122, Issue 2, page: 226 –226
- DOI: 10.1049/piee.1975.0055
- Type: Article
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New method for solving the energy-balance equation for moving-boundary a.c.arcs
- Author(s): H.E. Lee ; H.K. Messerle ; A.D. Stokes
- Source: Proceedings of the Institution of Electrical Engineers, Volume 122, Issue 2, p. 227 –231
- DOI: 10.1049/piee.1975.0056
- Type: Article
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The characteristics of moving-boundary a.c. electric arcs are derived using a new mathematical approach. The solutions, although approximate, are found in specific cases to give close agreement with results obtained by exhaustive numerical calculations based on finite-difference methods1 and by experiments.2 The main advantage of the new method, which is based on variational calculus, is a greatly simplified calculation procedure, obtained with no evident loss of accuracy. The results can be expressed analytically in similar terms to those of the Mayr model, and the model lends itself to general predictions of current-interruption behaviour, allowing for interaction with the external circuit.
Magnetic-flux and eddy-current distributions at epstein corner lap joints
- Author(s): G.E. Goode and J.E.L. Bishop
- Source: Proceedings of the Institution of Electrical Engineers, Volume 122, Issue 2, p. 232 –234
- DOI: 10.1049/piee.1975.0057
- Type: Article
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The magnetic-flux and eddy-current distributions in the neighbourhood of double-lap corner junctions between magnetic strips are investigated numerically. The results cover a wide range of material anisotropy and relative gap reluctance, but are restricted to linear dependence of B on H. Reverse flux transfer is predicted in some regions of overlap when the gap reluctance is low and the easy direction of magnetisation is perpendicular to the strip length. Corner corrections are provided for both permeability and loss measurements.
IEE Conference Publication 122. Engineering design: a key to the management of successful enterprises
- Source: Proceedings of the Institution of Electrical Engineers, Volume 122, Issue 2, page: 234 –234
- DOI: 10.1049/piee.1975.0058
- Type: Article
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Influence of the wavefront of impulse voltages on the sparkover of rod gaps and insulators
- Author(s): T.E. Allibone and D. Dring
- Source: Proceedings of the Institution of Electrical Engineers, Volume 122, Issue 2, p. 235 –238
- DOI: 10.1049/piee.1975.0059
- Type: Article
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The influence of the duration of the wavefront of an impulse voltage on the sparkover of rod gaps, up to 80 cm, and insulators has been determined for voltages of both polarities up to 500 kV and for times to crest from 2 to 140 µs. The pattern of sparkover as the wavefront (T1) increases is a complicated one; for small gaps, the positiveimpulse sparkover first rises and then falls as the wavefront increases, the reverse behaviour to that of large gaps.Withstand voltages follow curves similar in shape to those of the critical-sparkover-voltage curves as T1 varies, and the value of rod gaps for co-ordination of insulation tests is questioned. The effectiveness of a radiation source in sphere-gap voltage measurement is demonstrated and its use again recommended.
IEE Mersey & N. Wales Centre: Chairman's address. The engineer and the future
- Author(s): R.D. Haigh
- Source: Proceedings of the Institution of Electrical Engineers, Volume 122, Issue 2, p. 239 –240
- DOI: 10.1049/piee.1975.0060
- Type: Article
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Erratum: Field mapping using a computer: compensation for infinite space
- Author(s): P.A. Einstein
- Source: Proceedings of the Institution of Electrical Engineers, Volume 122, Issue 2, page: 240 –240
- DOI: 10.1049/piee.1975.0061
- Type: Article
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