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Electrical Engineers, Proceedings of the Institution of

Issue 10 • Date October 1974

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Displaying Results 1 - 25 of 31
  • Design of precision rectifiers using operational amplifiers

    Page(s): 1041 - 1044
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (360 KB)  

    Two new precision rectifiers, a halfwave circuit and a full wave circuit, are described. The circuitsemploy operational amplifiers to eliminate the effects of diode nonlinearity and diode-temperature dependence. The transfer characteristics of the two circuits are derived by analysis. Experimental results are also provided which show that the circuits operate accurately over a large dynamic range of input signals. View full abstract»

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  • Synthesis of high-stability 4th-order single-sideband crystal lattice filters

    Page(s): 1045 - 1050
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (522 KB)  

    A lowpass antimetric ladder network is transformed into a single-lattice single-sideband crystal filter using simple network equivalences and an asymmetrical frequency transformation. A methodis then given for altering the phase shift independent of both the attenuation and network configuration, and applied so that a crystal in each lattice arm resonates at the frequency of infinite attenuation. Transferring these crystals to outside the lattice results in single-sideband filters of high stability. A frequency transformation involving two attenuation poles is given in an Appendix. View full abstract»

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  • Power reciprocity in antenna theory

    Page(s): 1051 - 1056
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (749 KB)  

    A rigorous derivation of the power-reciprocity theorem in antenna theory is presented. It relates the absorption cross-section of the load in the receiving situation to the power gain of the antenna in the transmitting situation. The most general case is considered, namely (a) the materialof which the antenna is made may be lossy, anisotropic and inhomogeneous, if only linear in its electromagnetic behaviour, (b) the vectorial amplitude radiation characteristic of the antenna in the transmitting situation and the incident plane wave in the receiving situation may be arbitrarily elliptically polarised, and (c) the impedance of the load in the receiving situation may be arbitrarily mismatched to the input impedance of the antenna in the transmitting situation. Therefore the known, restricted form of the theorem is generalised; also some notions are made more precise. As a corollary, a generalised theorem is presented as to the average value of the absorption cross-section of the load taken over all directions of incidence. View full abstract»

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  • Transmission loss in a waveguide partially filled with dielectric

    Page(s): 1057 - 1058
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (251 KB)  

    The. problem is to calculate the dielectric loss in a waveguide partially filled across its smaller dimension. A numerical solution can be found which applies for any ratio of dielectric thickness to height of guide, but only when the dielectric loss is small. Numerical results agree with some obtained by previous authors. View full abstract»

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  • Frequency control using binary rate multipliers for automatic testing on c.w. radar systems

    Page(s): 1059 - 1066
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (875 KB)  

    R.F. signals with certain defined characteristics have to be generated for ground testing on f.m. c.w. radar airborne-guidance systems. Normally in flight, two r.f. signals would be received; one direct from the ground transmitter and the other originating at the same transmitter, but reflected from a target. A lowfrequency wide-deviation frequency modulator is applied to the carrier at the ground transmitter. Owing to a difference in the path lengths of the two signals, a difference in phase angle of the modulating signal results, and, owing to the Doppler effect, the carrier frequencies are slightly separated. For testing therefore two r.f. signals with a precise and variable difference frequency have to be generated. Also both signals must be frequency modulated at the same frequency to the same deviation, but with a variable phase angle between the two modulating signals. For this purpose, a study has been made of the behaviour of binary rate multipliers used partly to shift the frequency, and partly to frequency modulate the r.f. carriers. A common crystal oscillator would feed into two b.r.m.s each shifting the carrier by a different amount, and each frequency modulating the shifted carriers with the same deviation. The b.r.m. operates by removing pulses from an uninterrupted pulse train according to the digital address. Thus the mean output frequency is lower than the input, but is contaminated with phase jitter. Jitter magnitude varies considerably with the address pattern, and it increases with the number of address lines. A graph of maximum jitter is given for increasing numbers of address lines up to 13. It isshown how phase jitter may be reduced to an acceptable limit, and how a system to meet the requirements may be designed. View full abstract»

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  • Hybrid decoding for digital-communication-feedback systems

    Page(s): 1067 - 1075
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1162 KB)  

    Forward error correction (f.e.c.) and decision feedback (a.r.q.) are combined using a hybrid decoding scheme of partial error correction and partial error detection. This is shown to have advantages when a low error probability is required and efficient use of transmitter power is important. The performance of the scheme is analysed, assuming transmission over a channel disturbed primarily by white Gaussian noise. Results are presented for systems employing various BCH codes showing the effects on system performance of varying code length, code ratio, and of varying the maximumerror weight the decoder is allowed to correct. The hybrid scheme is shown to need less transmitter power than systems using either pure forward error correction or decision feedback with error detection alone, although the ability to reject error bursts is retained. A design procedure for choosing the code parameters and maximum error-correcting weight is given, and one method of implementing the decoding is suggested. View full abstract»

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  • Computer-controlled queuing system with switching network and blocked customers rejoin end of queue

    Page(s): 1076 - 1079
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (415 KB)  

    The paper presents a detailed study of a computer-controlled queuing system with Poisson input, firstcome first-served queue discipline, multiple exponential servers, switching network and blocked customers feedback to the end of the queue. A generating function for the stationary-state probabilities of the system and a necessary and sufficient condition for the existence of statistical equilibrium for the system are derived. Further, a formula for the determination of the waiting-time distribution in the system is obtained by the use of the theory of Markov chains. View full abstract»

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  • Computer-controlled queuing system with feedback and swap times

    Page(s): 1080 - 1085
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (605 KB)  

    The paper presents a detailed investigation of a computer-controlled queuing system with Poisson input, multiple exponential servers, first-come first-served queue discipline, feedback and fixed finite swap times. The swap time is the time needed for the allocated server to acquire necessary information about the customer to be served and set up a necessary connection. A generating function for the stationary state probabilities of, and the necessary and sufficient condition for, the existence of statistical equilibrium for the system are derived. Further, a formula for the determination of the waiting-time distribution in the system is obtained by the use of the theory of Markov chains. View full abstract»

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  • IEE Conference Publication 114. Electromagnetic-wave theory

    Page(s): 1087 - 1088
    Save to Project icon | PDF file iconPDF (268 KB)  
    Freely Available from IEEE
  • Generalised analysis of machine windings, impedances and generated e.m.f.s, with particular reference to multispeed synchronous machines

    Page(s): 1089 - 1098
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1194 KB)  

    The paper extends previously available results for the calculation of airgap flux densities, generated e.m.f.s and synchronous impedances for all types of salient-pole or segmented synchronousmachines. Special emphasis is placed on multispeed machines, both excited and unexcited, but results for single-speed machines are included as particular cases. Nonidentical phase windings are treated as is necessary for practical multispeed machines. The needs to allow, in fundamental-frequency power calculations, for pulsations in the magnetic potentials induced on the rotor, and for differences in phase associated with the different harmonics, are brought out and treated for the first time. Earlier studies of various types of single- and multispeed reluctance machines are correlated in the context of the generalised results presented. View full abstract»

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  • Linear induction motors as `electromagnetic rivers¿

    Page(s): 1099 - 1108
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1367 KB)  

    Conducting material, in both the solid and the liquid state, can be suspended above a.c. coil systems. It is shown how a rectangular plate, suspended by one such system, may also be propelled by the same system of currents which serve to suspend it, and that lateral guidance is then automatically built into the system. In early experiments which are described, over 90% of the input power to such a system was converted into heat in the process of suspension and guidance. Further inventions are then described, by means of which it is theoretically possible to convert the whole ofthe secondary input power to propulsion. It is concluded that such systems show promise for application to high-speed ground transport. View full abstract»

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  • Use of surface integral equations for analysis of TM-induction problem

    Page(s): 1109 - 1116
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (738 KB)  

    The problem considered is that of evaluating the induced fields and the power loss in a long conductor with arbitrary cross-section placed in a time-harmonic transverse magnetic (TM) field. Hitherto, the problem has been analysed by numerically solving the governing differential equations or a volume-type integral equation. The paper presents a new approach which uses Helmholtz single-and double-layer potentials to derive integral equations which relate the values of the axial current density and the tangential magnetic field at the surface of the conductor. These are two coupled Fredholm integral equations with weakly singular kernels. As an example, the eddy-current losses in a rectangular conductor placed in a uniform magnetic field are computed, and the results arecompared with previous ones. The proposed approach has two salient advantages. First, by reducing the dimensions of the problem by one, the computation time is considerably reduced. Consequently, many problems that are beyond the practical limit of previous approaches can be easily handled. Secondly, both magnetic and nonmagnetic conductors can be handled. View full abstract»

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  • Equivalent circuits from electromagnetic theory low-frequency induction devices

    Page(s): 1117 - 1121
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (698 KB)  

    A method is described for rearranging the electromagnetic-field-theory solutions of certain low-frequency devices into equivalent-circuit form. Two types of equivalent circuit are described, one `basic¿ the other `terminal¿. An equivalent circuit can aid the understanding of a device, and it also makes possible substantial saving in computer time. To illustrate the method, the equivalent circuit of one type of cylindrical induction device is derived. Finally, a list is given of other devices for which equivalent circuits have been developed. View full abstract»

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  • Performance analysis of diecast multicage induction motors: a comparative study of two approaches

    Page(s): 1122 - 1126
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (460 KB)  

    The paper presents a comparative study of the analysis of diecast double-cage induction motorsby single-cage/deep-bar approach and multicage-approach methods. In both the methods, saturation ofleakage flux paths and main flux paths have been considered. The performance of individual cages and saturation effects have been clearly brought out. The skin-effect ratios for the rotor, obtained by both the methods, are compared. The validity of the equations is ascertained by comparison with the experimental results. View full abstract»

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  • Calculation of saturation effects in segmented-rotor reluctance machines

    Page(s): 1127 - 1133
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (699 KB)  

    There have been many recent developments in the design and analysis of segmented-rotor reluctance motors but no convenient method of allowing for the effects of saturation has been published. The paper presents a method of analysis based upon the simplifying assumption of a limiting value of radial airgap flux density. It is shown that, by means of the method presented, experimentally observed saturation effects may be predicted. View full abstract»

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  • Control of dual-excitation generator using derivatives of rotor angle

    Page(s): 1134 - 1140
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (741 KB)  

    The paper investigates the performance of a synchronous generator with two field windings, with separate voltage and angle regulators. The effects of continuous rotor velocity and acceleration feedback signals in the regulator loops are examined, and it is shown that different derivative gains must be used during steady-state and transient conditions to obtain the best performance. This is achieved by the introduction of some simple switching in the angle regulator, and is most effective when implemented at the peak of the first rotor-angle swing. Acceleration feedback is introduced in the governor system, and the results illustrate the significant improvements in transient performance which are possible with the fast governor systems which have been developed recently. Initial results were obtained by digital computer, and the proposed control schemes were then tested on a laboratory micromachine system. View full abstract»

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  • Extension of stable operating regions of synchronous machines using low-sensitivity excitation control

    Page(s): 1141 - 1145
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (525 KB)  

    In the usual design of optimal linear regulators for synchronous machines, the controller is designed for a particular set of system operating conditions. However, in actual system operation, these conditions are subject to load demands. Consequently, the optimal controller designed for a certain operating condition will no longer yield a satisfactory performance at others. The paper endeavours to overcome this problem by proposing a method for designing optimal controllers with low sensitivity to systemloading conditions, while avoiding the complexity of the resulting controller structure. A numerical example involving a synchronous machine swinging against an infinite busbar is used to demonstrat the usefulness of low-sensitivity controllers in extending the stable operating region. View full abstract»

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  • Improvements in phase-controlled circulating-current cycloconverter using communication principles

    Page(s): 1146 - 1149
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (368 KB)  

    The paper demonstrates the application of communication techniques to improve the phase-controlle circulating-current cycloconverter. A modification to the existing cosinusoidal firing method is proposed which employs regular sampling instead of natural sampling. It is shown that this modification leads to a reduction in the magnitude of certain (low-frequency) harmonics that exist in the output waveform of the conventional cycloconverter. It is concluded that this may lead to an extension of the useful frequency range of the cycloconverter. View full abstract»

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  • Computerised linear control of a.c. generator power output

    Page(s): 1150 - 1154
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (498 KB)  

    The paper describes an online control system for regulating the power generation of an alternator that is connected to the supply Grid. The voltage, current and power factor of the a.c. generator are sampled and fed to the computer via analogue-digital convertors. The limits of the range of frequencies for sampling the input parameters to the computer are investigated, and an expression for the transfer function of the a.c. generator is derived. The input parameters are processed to produce the power, power angle and torque of the a.c. generator. The correcting signal from the computer is fed to the control field of a d.c. servomotor via a digital-analogue convertor. The servomotor in turn regulates the throttle opening of the petrol engine, which drives the a.c. generator. The piecewise linear method is used to approximate the relationship between the output of the a.c. generator and the throttle opening of the engine, and the technique of dynamic programming is used to optimise the overall system. Satisfactory results are obtained on an experimental system which regulates the output and stability of a 5 kVA petrol-engine/a.c. generator set. View full abstract»

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  • Steady-state phase-variable model of the synchronous machine for use in 3-phase load-flow studies

    Page(s): 1155 - 1164
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (972 KB)  

    The derivation of a steady-state phase-variable model of the synchronous machine is considered for the purpose of investigating the influence of machine saliency on the unbalanced behaviour of powersystem networks. The model is particularly relevant as a means of representing the salient-pole generators of important hydroelectric stations feeding large and remote load centres. Application of the model is also considered so that corresponding blocks of the system Jacobian matrix are formulated and used in a previously described Newton ¿ Raphson algorithm to obtain 3-phase load flows. The results of computation illustrate that saliency is not an insignificant parameter amongst those which determine the extent and distribution of system unbalance. View full abstract»

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  • Computer-program description. Power-system dynamic-simulation program

    Page(s): 1165 - 1167
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (319 KB)  

    A special-purpose program is described for simulating power-system dynamic response. The program allows detailed study of the effects of generators, excitation systems and turbine-governor systems on power-system transient and dynamic stability. The main feature, which has been emphasised in the program design, is flexibility in the modelling of the generators and their controllers. The program is very efficient for repetitive studies of small or moderate sized systems, and allows for a high degree of user interaction. View full abstract»

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  • Proposals for installation practice of single-core cables

    Page(s): 1168 - 1174
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1042 KB)  

    A review of installation techniques has been undertaken for single-core power cables employed in the cable networks of industrial plant. Particular attention has been given to the performance of trefoilcable groups under short circuit, and the influence of the consequential electromagnetic forces on the supporting and securing system used to hold the cables. For the investigation, a series of short-circuit tests have been carried out, subjecting a range of typical cables to currents up to 44 kA. Based on these tests, proposals are made for securing cables using ties at spacings chosen over a range 0.3 m¿1.2 m, with cleats spaced at 4 m and main supports at 2 m. View full abstract»

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  • Damping of aeolian vibration on overhead lines by vibration dampers

    Page(s): 1175 - 1179
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (573 KB)  

    A new method is presented for determining the effectiveness of dampers used to suppress aeolian vibration on overhead lines. The method is applied to a Stockbridge damper and a simple picture is presented of the way in which this damper works. A second type of vibration damper is also considered, to demonstrate the way in which the performance of different dampers can be evaluated and compared using the new method. View full abstract»

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  • Summary: Comparative performance of amplitude-comparator pilot-wire differential-protection systems

    Page(s): 1180 - 1182
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (427 KB)  

    A new relay circuit, applicable to asymmetrical pilot circuits, is described. In the steady state for relays at both ends, the circuit provides identical unit-diameter circular stability areas on the complex plane, centred on (1, 0), and it is suggested that this relay circuit constitutes a preferred characteristic of marginal operation. Certain alternative relay configurations are compared, to ascertain relative susceptibilities to the effects of induced interference voltages and the presence of d.c. components in the relaying quantities derived from the protected system. Homogeneous pilot circuits are assumed for simplicity, and the relay schemes considered include: (i) that referred to above which provides the preferred relay characteristic (ii) that which provides termination of the pilot circuit in characteristic impedance (iii) that which provides compensation for pilot-circuit phase-shift and a self-inverse characteristic. 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.

Full Aims & Scope