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Electrical Engineers, Proceedings of the Institution of

Issue 12 • Date December 1975

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Displaying Results 1 - 25 of 30
  • Susceptance-slope parameter of waveguide partial-height ferrite circulators

    Publication Year: 1975 , Page(s): 1329 - 1332
    Cited by:  Papers (11)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (377 KB)  

    The paper derives approximate eigennetworks for the demagnetised counterrotating modes of partial-height ferrite-waveguide circulators. The susceptance-slope parameter obtained from these eigennetworks is found to be in good agreement with experimental results at S-, X- and J-bands, and may therefore be used either for analysis or synthesis. Since the gyrator conductance of the circulator is known once the susceptance-slope parameter is obtained, a knowledge of the latter variable makes feasible the complete description of the junction. These networks are constructed in terms of a distributed resonator that determines the operating frequency of the device, and an ideal transformer which is defined by the impedance change between the junction and the input waveguide. View full abstract»

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  • Analysis of effect of fabrication errors on performance of surface-acoustic-wave m-sequence correlators

    Publication Year: 1975 , Page(s): 1333 - 1338
    Cited by:  Papers (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (809 KB)  

    The paper describes in detail the statistical analysis used in a study of the degradation produced by imperfections in surface-acoustic-wave correlators. We consider the effect of errors in either one or both of the generator/detector pair when the input signal is either a single or a periodic m-sequence. A theoretical model, which incorporates taper, band limitation, random amplitude variations and spurious signal level, accounts for a large measure of the experimentally observed degradation of performance. View full abstract»

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  • Slow-wave propagation in a rectangular waveguide

    Publication Year: 1975 , Page(s): 1339 - 1343
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (608 KB)  

    A theoretical and experimental investigation of the conditions required for the support of the dipole mode as a slow wave inside a rectangular channel is presented. From this a number of conclusions can be drawn. First, it can be concluded that the wall structure, both the bare-metal and grid surfaces, presents to the adjoining field anisotropic impedances significantly different from those which might have been expected from planewave considerations. Secondly, the attenuation and phase-change behaviour can vary, according to boundary conditions, over a wide range of slow waves, and possibly extending to fast waves in some cases, with losses in the 3 GHz region that are of the same order as those of an equivalent TEM line. Thirdly, that a sudden transition can be traced from a transverse evanescent E1n field in the waveguide, when it is open-sided, to a dipole configuration freely propagating when closed by a grid structure. And, fourthly, that the wave can be usefully applied not only to lines employed for ordinary transmission, but also, in cases where coupling is required en route, to an adjacent circuit. Alternatively, by suitable design, it can be used for delay lines. View full abstract»

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  • Solution of Maxwell's equations in three space dimensions and time by the t.l.m. method of numerical analysis

    Publication Year: 1975 , Page(s): 1344 - 1348
    Cited by:  Papers (51)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (554 KB)  

    The paper shows how a general 3-dimensional medium may be represented by a simple model made up of generalised 2-dimensional nodes. It is then shown how this model may be used for the numerical solution of electric and magnetic vector fields within the medium, without any mathematical formulation of the problem. Results for the resonant frequencies and power decay times of some cavities partially filled with dielectric are given using this method. There has been an excellent agreement in all cases where comparisons could be made. View full abstract»

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  • Generalised elements for t.l.m. method of numerical analysis

    Publication Year: 1975 , Page(s): 1349 - 1352
    Cited by:  Papers (15)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (476 KB)  

    The paper shows how the conduction term in Maxwell's equations can be introduced into the t.l.m. method of numerical analysis. The use of series nodes is also examined, thus laying the foundations for the development of the general 3-dimensional t.l.m. method. View full abstract»

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  • Gain enhancement of microwave antennas by dielectric-filled radomes

    Publication Year: 1975 , Page(s): 1353 - 1358
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (706 KB)  

    Structural constraints can require that the space within a radome can be filled with a rigid lightweight material, and the question arises as to whether the presence of this material can improve, rather than impair, the performance of the associated microwave antenna. Using a simplified model based on rectangular geometry, it is shown that a slab of material having an appropriate relative permittivity can increase the antenna gain by 3¿7 dB for typical cases. Computations carried out using modal methods indicate that there is a pronounced periodic gain variation with slab length; this is confirmed by experiment for both planes of polarisation. The practical implementation of the enhancement technique is discussed and illustrated by typical airborne radar applications. Loss effects in the dielectric material are shown to be negligible and some simplified design data relevant to linear arrays are compiled in an Appendix. View full abstract»

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  • Asymptotic methods for the prediction of dual-reflector-antenna efficiency

    Publication Year: 1975 , Page(s): 1359 - 1362
    Cited by:  Papers (2)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (466 KB)  

    Evaluation of the image-region field from dual-reflector antennas using the physical-optics approximation is impractical when the main reflector is large. Because of this, efficiency calculations have previously relied on geometrical optics to provide the scattered field from the main reflector. A more realistic assessment of this scattered field is obtained by the inclusion of edge diffraction from the main reflector. This can be derived either from the geometrical theory of diffraction or by an asymptotic expansion of the physical-optics integral for the main reflector. For the present application, where the scattered field is required on the subreflector surface, these two methods are shown to be comparable. It is shown that the calculated efficiency for a dual-reflector antenna capable of beam scanning can be significantly modified by the inclusion of this edge-diffracted field. Evaluation of the image-region field from dual-reflector antennas capable of beam scanning can be significantly modified by the inclusion of this edge-diffracted field. View full abstract»

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  • Low-frequency correlator using a bucket-brigade analogue delay line

    Publication Year: 1975 , Page(s): 1363 - 1366
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (392 KB)  

    The paper describes a low-frequency correlator in which a continuously varying delay of a signal is obtained by means of a bucket-brigade analogue delay line. Experimental results of the successful application of the correlator to the areas of autocorrelation, impulse response and signal recovery are given. View full abstract»

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  • Topological derivation of the state equation of networks containing commensurate transmission lines

    Publication Year: 1975 , Page(s): 1367 - 1371
    Cited by:  Papers (6)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (470 KB)  

    Active networks whose only state elements are commensurate transmission lines are analysed using topological methods. The state equations of these networks are derived in explicit form and four output equations are derived, depending on the choice of the output vector. No restrictions on the topology of the networks are required for the existence of these forms. An example of the applications of the results is given. View full abstract»

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  • Discrete-time queuing system with instantaneous defection and service interruption

    Publication Year: 1975 , Page(s): 1372 - 1376
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (537 KB)  

    The paper presents a detailed analysis of a discrete-time queuing system with binomial input, first-come firstserved queue discipline, single server and with both instantaneous defection and service interruption. The repair times of the server are assumed to be identically distributed, independent, positive random variables with a general distribution. The service interruption is subject to binomial probability distribution. The generating functions for the queue length and waiting-time distributions are obtained. Using these generating functions, the mean queue length and mean waiting time are determined. It is shown that some results reported in the literature can be obtained from that in this paper as special cases. View full abstract»

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  • Orthogonality of i.t.m. and i.t.e. continuous modes

    Publication Year: 1975
    Save to Project icon | PDF file iconPDF (136 KB)  
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  • Computation of the magnetic field of permanent magnets in iron cores

    Publication Year: 1975 , Page(s): 1377 - 1381
    Cited by:  Papers (11)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (635 KB)  

    A method for computing the magnetic field of permanent magnets in the presence of iron cores is described. The method makes use of finite elements and allows for nonuniform magnetisation in the magnet and saturation in the iron if required. Two possible representations of the field in the magnet are compared. Some, simple examples are used in a study of the rate of convergence to a solution. View full abstract»

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  • Performance of linear induction motors with airgap windings

    Publication Year: 1975 , Page(s): 1382 - 1390
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (865 KB)  

    Conventional high-speed linear induction motors designed to operate from a 50 Hz supply possess large leakage reactances. This is because of the large end-winding-overhang/core-width ratio. The resulting poor power-factor performance of these machines may be improved by incorporating the primary end windings into the main magnetic circuit of the machine. Difficulties in construction and low airgap flux density point to the use of airgap windings. A mathematical model is developed, and verified against practical test results, to give the complete electrical and mechanical performance of axial-flux linear machines with 2-dimensional conductor distribution and airgap windings. The treatment makes no assumptions about input current balance. Any number of serially connected coil groups, energised from independent voltage sources, are considered. The model is also suitable for predicting the performance of conventional linear machines and in this case gives improved estimates over previous single-dimensional analyses. The model is used to predict the performance of two equivalent high-speed designs. These results show an improved power factor over a conventional design for an airgap-wound machine with a minimum of coil overhang. View full abstract»

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  • Acoustic noise from small 2-pole single-phase induction machines

    Publication Year: 1975 , Page(s): 1391 - 1396
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (687 KB)  

    The radial magnetic force waves in small 2-pole single-phase induction machines are investigated analytically, taking into account the interaction of the homopolar flux-density waves and conventional flux-density waves. The analysis is verified by noise and vibration measurements. Experimental studies are made on the effects of the unbalance between the main and auxiliary fields on homopolar flux-density waves and on noise emission. The effects of a number of design changes on noise levels are also studied. These include a reduction in m.m.f. harmonics, minimising the dynamic unbalance of the rotor and reducing the magnetic permeance variations in the stator and rotor cores. View full abstract»

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  • Analysis of d.c. series motor controlled by power pulses

    Publication Year: 1975 , Page(s): 1397 - 1398
    Cited by:  Papers (9)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (199 KB)  

    The main problem in the analysis of the chopper-fed d.c. series motor arises due to the nonlinear relation between the armature induced voltage and the armature current. Because of this, the differential euqations which describe the operation of the motor in different modes of a chopper cycle are nonlinear. Exact solution of these equations can only be obtained numerically by the use of considerable computation time. The paper describes certain approximations which permit the derivation of simple but accurate analytical methods for the analysis of the d.c. series motor fed by a chopper, with either pulse-width control or with current-limit control. View full abstract»

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  • Digital simulation of a group of induction motors

    Publication Year: 1975 , Page(s): 1399 - 1401
    Cited by:  Papers (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (410 KB)  

    The calculation of the transient currents, voltages, torques and speeds of a group of induction motors supplied from a common transformer, following switching operations or faults, is considered. The differential equations describing the system are numerically integrated, accounting for any discrete changes in the currents caused by the switching operations. The digital computer program is capable of dealing with all the possible sequences of symmetrical switching and fault conditions in a group of up to 10 motors and it incorporates the facility for automatically plotting the main results on an incremental graph plotter. The paper indicates the theoretical approach and describes the computer program. View full abstract»

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  • Improved technique for computation of power-system transient-stability regions

    Publication Year: 1975 , Page(s): 1402 - 1404
    Cited by:  Papers (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (279 KB)  

    The paper presents a simple technique for obtaining improved regions of transient stability of power systems. This requires a simple transformation of the system equation before Popov's; stability condition is employed for generating the Lyapunov function. Results are presented for computation of the regions of both absolute and exponential stability. View full abstract»

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  • Control communications and protection for the El Chocon-Buenos Aires 500 kV transmission system

    Publication Year: 1975 , Page(s): 1405 - 1415
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1606 KB)  

    The paper describes some of the main design objectives, the design features required to achieve these objectives and the appropriate operating experience associated with the communications, protection and automatic switching control for the Chocon 500 kV network. In particular, the paper highlights control measures necessary for a long e.h.v. transmission network subjected to wide variation in power transfer with upper limits approaching the steady-state stability limit. View full abstract»

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  • Synthesis of multiple systems switched with alternating polarity

    Publication Year: 1975 , Page(s): 1416 - 1419
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (434 KB)  

    The paper deals with multiple systems switched with alternating polarity (states±1). An algebra is presented for the combination of subsystems into a compound system without constraints on the switching functions of the former. The proposed method permits realisation and analysis of practical switching systems, e.g. polyphase systems under symmetric supply. View full abstract»

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  • Discussion on ¿Self-commutated rectifier to improve line conditions¿

    Publication Year: 1975 , Page(s): 1419 - 1420
    Save to Project icon | PDF file iconPDF (585 KB)  
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  • Dynamical performance of a single-phase thyristor a.c. regulator

    Publication Year: 1975 , Page(s): 1425 - 1430
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (980 KB)  

    The operation of a single-phase thyristor a.c. regulator is described in which thyristors are used to connect windings on a multiwinding transformer, so as to vary the amplitude of the regulator's output voltage. Independent control of the amplitude of either the positive or negative halfcycles of the output voltage allows the regulator to be considered as a 2-variable system. Minimum response can be achieved with the use of a controller which is time shared between subsystems, but this produces interaction between them. Time-series methods are used to identify the regulator when it is operated under these conditions and the system's stability bounds and decoupling conditions are defined. The regulator is decoupled to set-point input signals and output disturbances using state variable feedback and a `deadbeat¿ response in one cycle of the supply frequency is achieved. View full abstract»

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  • Control of an energy system using a multimodal control hierarchy

    Publication Year: 1975 , Page(s): 1431 - 1436
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (745 KB)  

    The paper describes a hierarchical multilevel control strategy for the optimal control of a complex energy system. The study is based on a refinery in the UK. The proposed control structure rationalises the operation of the overall system. View full abstract»

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  • Pole assignment with optimality and minimum eigenvalue sensitivity

    Publication Year: 1975 , Page(s): 1437 - 1438
    Cited by:  Papers (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (186 KB)  

    A method is presented for designing a constant-gain feedback controller for assigning the closed-loop poles of a linear system to specified locations while minimising an objective functional which is a linear combination of a quadratic performance index and an eigenvalue sensitivity functional. View full abstract»

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  • Evidence for transitions in the prebreakdown mechanism of liquid dielectrics

    Publication Year: 1975 , Page(s): 1439 - 1442
    Cited by:  Papers (8)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (544 KB)  

    Studies using both n-hexane and transformer oil stressed with direct voltage have indicated that, for nonuniform electric fields, cavitation may be produced together with associated gas-initiated light emission and acoustical disturbances. Transformer oil is shown to emit light below the cavitation-onset stress by an assumed electronic electroluminescence which is also invoked to explain light emission under uniform field conditions. Cavitation onset is shown to be strongly temperature dependent. Tests at elevated temperatures indicate that the discontinuities which were found in the conduction characteristics are not associated with bubble formation or collapse, and alternative explanations are offered. A distinction is drawn between the integrated conduction characteristics and the current pulse behaviour which accompanies the gas-phase disturbance in the liquid. 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.

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