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Electrical Engineers, Proceedings of the Institution of

Issue 9 • Date September 1975

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Displaying Results 1 - 20 of 20
  • Mirror corner for use in an overmoded circular-waveguide system

    Publication Year: 1975 , Page(s): 865 - 870
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (692 KB)  

    A method for turning the axis of propagation of a highly overmoded circular-waveguide system through a right angle is described. An open system using an ellipsoidal mirror reflects energy radiated from the aperture of a truncated length of circular waveguide and refocuses it in the aperture of a second circular waveguide placed perpendicular to the first waveguide. The method is shown to be capable of working over the range 30 to 100 GHz with low insertion loss View full abstract»

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  • Null method for measuring small dielectric loss at microwave frequencies

    Publication Year: 1975 , Page(s): 871 - 873
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (424 KB)  

    A method based on the use of a 4-port directional coupler provides an alternative to a method previously described. The specimen is a long bar in a waveguide, nearly filling it in the smaller direction; in the larger direction it may either nearly fill the guide or occupy a small central region. Reflections from the ends of the specimen are reduced by tapers, or by curved sections of guide, and their effects are then eliminated by averaging the results for a series of positions of the specimen. Imperfections of the directional coupler can be eliminated (if they are not too large) by the use of two positions of an auxiliary short circuit. For measuring loss in solids, the method is probably better than that described before, because it does not need a liquid of matching permittivity, which has proved difficult to find. View full abstract»

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  • Analogue-numerical approach to conformal mapping

    Publication Year: 1975 , Page(s): 874 - 876
    Cited by:  Papers (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (323 KB)  

    A highly efficient engineering approach is described for the calculation of capacitance using the Schwarz¿Christoffel equation but which avoids the need for complicated mathematical analysis. The method is suitable for the analysis and synthesis of transmission lines. View full abstract»

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  • Coaxial 2-port S-parameter system for transistor characterisation in three configurations from 1-500 MHz

    Publication Year: 1975 , Page(s): 877 - 886
    Cited by:  Papers (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1373 KB)  

    A description is given of a coaxial 2-port s-parameter measuring system for the characterisation of transistors in common base, common emitter and common collector configurations from 1 to 500 MHz. The system is inherently wideband, because no directional couplers or hybrids are used. The incident and reflected waves are derived from measurements of the total voltage across a coaxial line by direct contact with the inner conductor using a commercial vector voltmeter. A description is also given of a precision transistor jig that accepts transistors with 2.54 mm and 5.08 mm p.c.d. lead spacing, in any configuration, with negligible common-ground impedance. The apparatus is calibrated in terms of precision air-dielectric coaxial lines, but the overall system accuracy for active-device measurements is assessed by transforming the twelve 2-port parameters, in the three configurations, to the equivalent 3-port scattering matrix when rows and columns should sum to unity. Other checks are performed using a unique relationship between the six s11 and s22 2-port parameters which, according to theory, should also equal unity. Detailed results are given of measurements on a BF115 transistor at 500 MHz both in the passive and active states. It is concluded that overall system accuracy can be many times worse for active devices than one would expect from the accuracy of calibration and subsequent measurements on passive networks using the above check procedures. A typical 3×3 matrix of an active BF115 transistor is adjusted to sum to unity by an iterative process. The matrix is then retransformed back to the three 2-port matrices, and is compared with the initial measured parameters. View full abstract»

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  • Use of pilot tones for real-time channel estimation of h.f. data circuits

    Publication Year: 1975 , Page(s): 887 - 896
    Cited by:  Papers (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1305 KB)  

    The, results of three field trials are shown to confirm the proposed technique of real-time channel estimation by pilot-tone phase analysis, originally described in a previous paper [Proc. IEE, 1970, 117, (12), pp. 2209¿2215]. A circuit within the UK represented short-distance operation, a UK-Gibraltar link was used for medium-distance working, and a link from the UK to Mauritius gave a long-distance circuit. The data format for the trials was single-channel wideshift f.s.k. at 100 baud operation. View full abstract»

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  • A.C. security assessment

    Publication Year: 1975 , Page(s): 897 - 902
    Cited by:  Papers (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (759 KB)  

    The analysis of security assessment has evolved from load-flow techniques to evaluate system response for credible outages of transmission and generating plant or loss of loads. The a.c. security assessment described, based on a decoupled load flow, provides a better insight into the state of the system than does the conventional d.c. reactance model. The paper describes a.v.r. and governor representation for evaluation of voltage changes after a loss of generation, pickup of spare generation and analysis of split-network conditions. It also includes a phase-shifter representation which retains network symmetry, the use of sensitivity factors for an adjusted a.c.decoupled-load-flow solution which produces fast and accurate results and automatically maintains voltage and generating limits to specified values. It concludes by giving computation and storage time for a number of practical networks. View full abstract»

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  • Power-stabiliser design using pole-placement techniques on approximate power-system models

    Publication Year: 1975 , Page(s): 903 - 907
    Cited by:  Papers (4)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (531 KB)  

    This paper describes the theory and procedure for the design of a power stabiliser to improve the dynamic stability of the power system. The algorithm to obtain a reduced-order state-space model of the power system is developed. Using this reduced-order model, a pole-placement technique has been used to design the power stabiliser, which can be very easily practically implemented. The algorithm has been successfully applied to improve the dynamic stability of a simulated 360-busbar power system. It is shown that considerable improvement in system damping can be obtained over the uncompensated system. View full abstract»

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  • Internally force-cooled power cables; optimum working temperature in the range 70¿358 K

    Publication Year: 1975 , Page(s): 908 - 914
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1063 KB)  

    Current ratings are compared for both copper and aluminium conductors, internally cooled with a variety of coolants, working in the temperature range 70 K to above ambient. Capital and running costs are then estimated for optimised designs of cable cooled with some of the more promising of these coolants. It is shown that there is no economic advantage in the deep refrigeration of the conductors, and that the optimum temperature of of operation for a force-cooled cable is near to ambient. With 400 kV cables, the preferred coolant is a low-viscosity mineral oil. Water may also merit consideration as a coolant, but further study is needed of the problems of segregation from the dielectric, and design of feed joints and terminations. 1000 kV cables are also considered, but because of the high cost of reactive compensation, unit capital costs are higher than for 400 kV cables. The preferred coolant for 1000 kV cables is a low-viscosity mineral oil. With oil-cooled cables, some economic, advantage can be gained by refrigerating to coolant-inlet temperatures of down to about ¿40°C. View full abstract»

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  • Current rating of an airduct transmission line

    Publication Year: 1975 , Page(s): 915 - 916
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (250 KB)  

    A possible design is described for a 230 kV duct line incorporating three tubular conductors supported in a duct 2.5 m in diameter with air at atmospheric pressure as the dielectric. Thermal models have been developed to facilitate the computation of temperature and current rating. With the duct line completely buried, it is found that the duct/soil-interface temperature is the limiting feature on current-carrying capacity, whereas, with the duct water cooled, or situated above the ground surface, the conductor temperature is limiting. For buried systems, the rating is only adequate, but with above-ground installation or intense water cooling of the buried duct, currents of the order of 10000 A may be achieved. View full abstract»

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  • 3-phase sudden-short-circuit analysis of an asynchronised synchronous machine

    Publication Year: 1975 , Page(s): 917 - 918
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (239 KB)  

    The paper outlines the development of expressions for the transient armature and field currents of an asynchronised synchronous machine (a.s.m.) following a sudden 3-phase short circuit. The field time constant of such a machine may be deliberately reduced by feedback, so that the desirable operating characteristics are obtained. The transientcurrent expressions are therefore derived for different values of this time constant, and comparisons are made between theoretical and experimental results for a 2 kVA machine. View full abstract»

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  • Determination of the parameters and parameter variations of a 3-phase induction motor having a current-displacement rotor

    Publication Year: 1975 , Page(s): 919 - 921
    Cited by:  Papers (13)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (339 KB)  

    The paper describes a method of determining the parameters and parameter variations of a 3-phase cage induction motor having a current-displacement rotor. The method is based on the use of the Newton-Raphson procedure for the solution of two nonlinear equations in two unknowns, these being the rotor resistance and leakage reactance at any particular rotor frequency. View full abstract»

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  • Thrust and normal forces in a segmented-secondary linear reluctance motor

    Publication Year: 1975 , Page(s): 922 - 924
    Cited by:  Papers (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (396 KB)  

    The linear counterpart of a segmented-rotor reluctance motor is studied to assess the feasibility of its application in ground transportation. Reactance formulas for the segmented-rotor motor are adapted to the segmented-secondary linear motor, and its performance is calculated using the salient-pole synchronous-machine theory. A numerical example of a preliminary design and analysis is presented, and the pertinent characteristics of the linear reluctance motor for ground transportation are discussed. View full abstract»

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  • Discussion on ¿Estimation of maximum demand on a British electricity-board system. Forecast periods of 1¿3 years¿

    Publication Year: 1975 , Page(s): 924 - 925
    Save to Project icon | PDF file iconPDF (617 KB)  
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  • Discussion on ¿Distance-relay performance as affected by capacitor voltage transformers¿

    Publication Year: 1975 , Page(s): 926 - 928
    Save to Project icon | PDF file iconPDF (545 KB)  
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  • Self-tuning controller

    Publication Year: 1975 , Page(s): 929 - 934
    Cited by:  Papers (153)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (814 KB)  

    A strategy for the design of self-tuning controllers of systems with constant but unknown parameters is presented. A cost function which incorporates system input, output and set-point variations is selected, and a control law for a known system is derived. This control law is shown to comprise a least-squares predictor of a function related to the cost function, and the control input is chosen to make the prediction zero. The parameters of the control law for the unknown system are estimated using a recursive-least-squares algorithm, and the optimal parameters are shown to be a fixed point of the algorithm. Whilst retaining their computational simplicity, the proposed method has several advantages over self-tuning-regulator strategies which attempt to minimise the output variance alone: weighting of control is allowed for; set-point variation may be optimally followed; there is no requirement to choose a system-related parameter to ensure convergence; and, for stable but nonminimum phase systems, there is no need to employ time-consuming methods, such as the solution of a Riccati equation. Several simulated examples are used to demonstrate the potential of the method. View full abstract»

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  • First and second-order-like structures in linear multivariable-control-systems design

    Publication Year: 1975 , Page(s): 935 - 941
    Cited by:  Papers (2)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (709 KB)  

    With the philosophy that many physical multivariable systems can, for the purposes of control-systems design, be approximately represented by much simpler forms, and that the analysis of such models can provide valuable insight into the time and frequency-domain characteristics of the system, the paper provides an analysis of two types of multivariable structure and derives closed-form solutions for proportional and proportional plus integral feedback controllers. The structures considered are shown to be direct multivariable generalisations of the classical 1st-order lag and the classical unity rank, minimum phase, overdamped 2nd-order system. View full abstract»

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  • The scanning electron microscope and other electron-probe instruments

    Publication Year: 1975 , Page(s): 942 - 946
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1014 KB)  

    First Page of the Article
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  • Passive network as a complex-voltage generator in four quadrants

    Publication Year: 1975 , Page(s): 947 - 950
    Cited by:  Papers (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (585 KB)  

    In single-channel and multichannel measurement systems, operating at an audio or low radio frequency, it is often necessary to adjust either the polar or cartesian components of the voltage in one or more of the channels to establish an initial set of conditions. A passive network is described that provides independent and precise control of the real and imaginary components of its output voltage. It can also be used as a generator of a complex voltage in any of the four quadrants with similar control of the cartesian components from a zero condition. Alternatively, if the real and imaginary components of the network's output are fed to a suitable sine/cosine potentiometer, the output voltage can be adjusted continuously in phase with constant modulus, and the latter parameter can be controlled independently by means of an attenuator. A brief description is given of the results obtained with an experimental network that was constructed to prove the theory at 1 MHz. A modified Kelvin-Varley voltage divider is also described that provides equal voltage increments with a constant voltage overlap between adjacent steps. If three capacitors in the network are switched, then it can be made to cover at least three decades in frequency. It is suggested that, for the frequency range from 50 Hz to about 50 kHz, when operating in the complex-voltage-generator mode, it could replace the mutual inductance of the conventional quadrant potentiometer. Also, in the case of multiport network analysers, operating at a fixed intermediate frequency, it could be used as an analogue vector voltmeter, in which the generated voltage is nulled against the network's response voltages. A further possible application is to precision inductance voltage dividers for either error-signal cancellation or the intercomparison of dividers of this type. View full abstract»

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  • Joule heating as the cause of erosion of copper cathodes of atmospheric arcs

    Publication Year: 1975 , Page(s): 950 - 951
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  • Magnetic properties of Alcomax III with dynamic excitation

    Publication Year: 1975 , Page(s): 951 - 952
    Cited by:  Papers (3)
    Save to Project icon | PDF file iconPDF (268 KB)  
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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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