DOI:10.1049/pi-2.1950.0165

出版商:IEE    

年代:1950

数据来源: IET

摘要:

A knowledge of the rate of change of frequency of a supply system is a useful addition to the information generally available in control rooms. At times when the available generating plant is inadequate to meet the prospective peak-demand, it assists in the recognition of critical conditions, and thus enables the necessary action to be taken to meet these conditions.The instrument described in this paper consists essentially of a sensitive frequency-meter: changes in frequency over successive fixed timeperiods are used to obtain values for the mean rate of change of frequency over these periods.The frequency-meter section of the instrument consists of a frequency-sensitive bridge network which is made continuously selfbalancing by means of a servo motor. The servo motor is controlled by the out-of-balance voltage from the bridge and itself controls the variable-impedance bridge elements necessary to maintain balance.The rate-of-change-of-frequency display unit depends for its operation on the measurement of the angular rotation of the servo-motor shaft in successive equal intervals by rotary voltage-dividers driven by the motor.The main design features are described, together with details of operation and performance of the instrument.

DOI:10.1049/pi-2.1950.0166

出版商:IEE    

年代:1950

数据来源: IET

摘要:

After describing the scope of protective earthing and the various methods available, the paper sets out a method by which the amount of protection afforded by each method may be evaluated from a knowledge of the incidence of those types of fault which contribute to the risk of shock. The cost of applying each method is established, and risks are calculated on the basis of available information of the incidence of faults. The systems are then compared on the basis of the amount of protection afforded for a given expenditure. Recommendations are made for the alleviation of the conditions under which protective multiple earthing may be utilized in Great Britain.

DOI:10.1049/pi-2.1950.0170

出版商:IEE    

年代:1950

数据来源: IET

摘要:

The light output of high-power daylight signalling lanterns of the non-directional type for marine use depends on the light output of the source itself, since only a small gain can be obtained from any optical system without restricting the angle of beam divergence. Incandescent lamps and carbon arcs both have limitations as high-power signalling sources, but the high-pressure mercury-vapour lamp has peculiar advantages.The paper records the history of the application of this lamp to daylight signalling equipment. It describes the various types of discharge-lamp signalling equipment which have been used. In the latest type, no mechanical shutter is employed, as the arc is ignited instantaneously by a high-voltage impulse circuit operated by the signalling key.

DOI:10.1049/pi-2.1950.0173

出版商:IEE    

年代:1950

数据来源: IET

摘要:

If the input information fed into a servo mechanism is only available at discrete intervals, the standard methods of servo design may be inadequate, especially if the interval periods are comparatively large. This paper introduces a method of handling the problem by utilizing cascaded integrators to generate polynomials. The error signals, measured at each interval point, are used to modify the coefficients of the polynomials in such a way that the input information may be more and more correctly handled.Assuming ideal integrators, it is shown that the optimum values of the control parameters of the system satisfy a general law; it is further demonstrated that, for a given interval period and number of integrators, the theoretical errors at each interval point can be calculated for any continuous analytical or tabulated input function. The problem of unequal interval periods is also briefly considered.Tests on a Meccano model and large-scale differential analyser have confirmed the theory and indicated that the effect of inaccuracies in instruments are appreciably reduced by the correction system. The arrangement is also shown to be a very effective rate-measuring device—a property which may be of value in certain process-control systems.Some ideas on the problems involved in designing a pulse-monitored servo system are considered, and a brief description is given of an electrical 2-integrator pilot model which has been constructed. It is stressed that the development of such systems is in an early stage, and some of the problems to be tackled in the future are therefore outlined.

DOI:10.1049/pi-2.1950.0176

出版商:IEE    

年代:1950

数据来源: IET

摘要:

The paper reviews the development of electric railway traction in France since 1900, and gives an account of the effect of the Government recommendations during the coal crisis following the First World War.The position of electrification at the outbreak of the Second World War is summarized, and this is followed by the technical reconstruction and re-equipment programme drawn up by the Societe Nationale des Chemins de Fer Francais.Particulars are given as to the physical nature of the electrified lines and the classes of traffic operating over them, together with a description of the method of power generation and distribution and details as to the spacing of the substations and the equipment installed.Other Sections are devoted to details of the various classes of electric locomotive and rail-car in service and to the factors which have contributed to their development.The paper also describes experiments which are being made in the use of a single-phase 50-c/s supply, and the problems which it presents, and gives particulars of three experimental locomotives which are being built for operation on this system.Finally, some operational statistics and a description of the latest S.N.C.F. express electric locomotive No. 7001 are given in an appendix.

DOI:10.1049/pi-2.1950.0186

出版商:IEE    

年代:1950

数据来源: IET

摘要:

The transductor is a fairly recently rediscovered simple electrical device of considerable adaptability and usefulness in a wide range of electric circuit techniques. The mechanical structure of a transductor is analogous to that of an iron-core transformer, but electrically the device is a d.c.-controlled ferromagnetic-core inductor of variable effective impedance, the impedance being changed by altering the magnitude of the controlling direct current. A transductor is fundamentally an a.c. apparatus which may be designed to operate, with either laminated or wound-strip core, at frequencies up to about 20 kc/s.Transductors are at present successfully employed as economically and technically efficient apparatus: (a) in heavy-current engineering for manually and for automatically operated power control in a great variety of specific modes, for measurement of heavy direct current and of high direct voltages, for remote control and for telemetering; and (b) in light-current engineering for magnetic amplification of weak direct currents for precision instrument work, computer circuits, servo mechanisms, and various other types of automatic control and of metering.The published literature of approximately the past 10 years is summarized to give a picture of transductor performance and of typical circuit applications.

DOI:10.1049/pi-2.1950.0187

出版商:IEE    

年代:1950

数据来源: IET

摘要:

The paper describes experiments designed to measure capacitance change by the variation produced in the frequency or phase of a signal from an oscillator normally of high frequency-stability. The advantages of such a method are tabulated, and the factors limiting the sensitivity and stability noted. In the experiments the sensitivity was increased by a process of frequency multiplication and frequency changing. An initiating oscillator designed to reach a high frequency-Stability at one particular frequency of operation is described. The auto-synchronized oscillator was adopted as a frequency discriminator with a high sensitivity but with restricted linear operating range. Results are given which indicate that capacitance changes of 5×10−4μμF were measurable with a possible error of ± 50%. Simple experiments to study the method for possible use in the measurement of capacitance changes occurring in about one millisecond are described.

DOI:10.1049/pi-2.1950.0188

出版商:IEE    

年代:1950

数据来源: IET

摘要:

The paper describes an electronic speed control which has been fitted to one of the two ship-model testing tanks at the National Physical Laboratory. A description of certain aspects of ship-model testing is included in a discussion of the reasons for fitting electronic control and of the performance required of such a control. The control system is a particular application of closed-loop automaticcontrol technique. A general description of it includes full details of those features which are special to this particular application, and a mathematical analysis of the design. Some typical test results obtained are shown in the form of graphical records and Tables.

DOI:10.1049/pi-2.1950.0189

出版商:IEE    

年代:1950

数据来源: IET

摘要:

Mercury-arc rectifiers for the conversion of power from alternating to direct current became familiar just after the First World War. Favourable results in operation led to rapidly increased numbers of mercury-arc-rectifier plants in service, especially when a.c. power distribution replaced individual local d.c. generating systems.By 1935 several well-known types of multi-anode mercury-arc rectifiers were being made by Continental manufacturers, each equipment consisting, in general, of a transformer and one, or several, multianode valves with appropriate auxiliary, controls and switchgear. This paper deals only with the valves commonly called rectifiers.About this time a critical point occurred in Continental mercury-arcrectifier technique in so far as definite limits for the multi-anode system, then exclusively used, appeared to have been reached. Attention was directed to the possibilities of building rectifiers using excited single anodes, as distinct from the American development of the ignitron, in which the anodes were similarly separated in individual selfcontained units.A brief review of the development and characteristics of glass-bulb and steel-tank multi-anode rectifiers is followed by a survey of the main theoretical and practical considerations affecting rectifier design, from which some general design rules are evolved. A description is given of experimental single-anode rectifiers which were designed and built in accordance with these principles, and the further development of the single-anode rectifier for low and high voltages is also outlined. A comparison is made of the characteristics of this type of rectifier and typical multi-anode steel-tank rectifiers.The problems of ionization and plasma-current relations are treated theoretically in appendices.

DOI:10.1049/pi-2.1950.0190

出版商:IEE    

年代:1950

数据来源: IET