摘要:

The general principles of thyratron control are discussed, the various points of difference between circuits being mentioned, together with some recently introduced improvements.Two valves are connected in reverse parallel, in series with the load. The brightness is controlled by varying the period of conduction of the valves, the ignition angle being varied by grid phase control. Hotcathode lamp filaments must be continuously heated from a separate current supply. Each lamp requires a separate ballast. Cold-cathode lamps require normal leakage-flux transformers only. Reduction of light to 1% or 2% of its maximum value is obtained with simple circuits, but improved stability can be obtained with special ballast arrangements which give a further reduction of light by an approximate factor of 10. Power factor can be corrected on the load side of the dimmer, with improvement in dimmer load rating and increased flexibility of use. Waveforms illustrating proper circuit conditions and various modes of malfunctioning are included.

DOI:10.1049/pi-2.1954.0126

出版商:IEE    

年代:1954

数据来源: IET

摘要:

The object of the paper is to recommend a simple, effective and co-ordinated scheme whereby any portable and transportable industrial electrical equipment can be used with a high degree of safety. In the early sections conclusions are drawn regarding the severity of the shocks which may be expected at different voltages and under different conditions, and a special note is made of the value from a safety point of view of limiting the duration of any medium-voltage shock to a few thousandths of a second. Typical a.c. supply systems are then studied to determine the voltage likely to appear on the earthed metalwork of protected equipment under fault conditions.Following a critical review of possible safety measures it is suggested that the use of extra-low voltage should be confined to handlamps, and that all portable tools should be supplied at 110 volts from fixed transformers in which the mid-point of the secondary is earthed. For transportable equipment, which may require considerable power, low voltage is unsuitable, and the use of medium voltage is recommended, provided that it is controlled by a circuit-breaker designed to trip instantly if any break should occur in the equipment earth-connection or in the event of an earth fault on the transportable equipment or its flexible cable. Two simple and inexpensive types of control units, developed for the Engineering Equipment Users Association, are described. Finally, stress is laid on the importance of regular maintenance and the use of reliable equipment.

DOI:10.1049/pi-2.1954.0127

出版商:IEE    

年代:1954

数据来源: IET

摘要:

The use of aluminium as an alternative to lead for power-cable sheaths became a focus of attention to cable makers and users as a result of drastic curtailment of supplies and increase in price of lead which took place after the 1939-45 War. During the past six years significant progress has been made in its employment, and to-day several thousands of miles of aluminium-sheathed cables are in service. The paper reviews the development and assesses the value of aluminium as a sheathing material against a background of test performance and operational experience. Beginning with a brief summary of aluminium production and consumption figures, the paper proceeds to discuss qualities of the metal in relation to cable-sheath requirements. The historical background of aluminium sheathing is outlined and a brief description is given of the tube-sinking process originated in 1947. Standard sheath thicknesses of aluminium-sheathed cables manufactured by the tube-sinking process are recorded, their mechanical and electrical characteristics and performance are surveyed, and the advantages deriving from light weight and mechanical strength are presented. An account is then given of installation procedure and operating experience, including analysis of failures encountered in service and methods of dealing with jointing, corrosion protection and sheathexpansion problems. The authors claim that aluminium has been established as a technically suitable and economic sheathing material to replace lead, and that its availability at an economic level constitutes an important asset to the cable industry.

DOI:10.1049/pi-2.1954.0130

出版商:IEE    

年代:1954

数据来源: IET

摘要:

Recent progress in the application of electricity to medical science is reviewed. The use of electronic techniques is characteristic of modern practice, and the applications to diagnosis and therapy are described together with details of the equipment, evolution and design. Alternative principles are listed and indication is given of any outstanding design problems. Maintenance is discussed and the trends of future development are indicated.No attempt is made to include items under the general classification of radiography or the many minor improvements in thermal or illuminating devices, although these form an essential part of modern hospital equipment.

DOI:10.1049/pi-2.1954.0133

出版商:IEE    

年代:1954

数据来源: IET

摘要:

A modified d.c. permeameter is described which, while retaining the refinement of separate compensating m.m.f. for flux leakage, does not involve the usual tedious and time-consuming measurements.A saturable-inductor type of field-measuring device is used to give automatic and continuous indication of the required compensatingcoil current at all points on the B/H curve or loop. Values of H from 10−3oersted upwards may be measured.

DOI:10.1049/pi-2.1954.0134

出版商:IEE    

年代:1954

数据来源: IET

摘要:

The modes of action of the parallel, bridge and centre-tap transductor connections are explained, and factors influencing the choice of circuits are discussed.Theoretical expressions are derived for the sensitivity and timeconstant under idealized conditions, and are considered for design purposes. Methods of controlling the transductor gain are briefly discussed.The paper discusses the use of push-pull transductor pairs, to obtain magnetic amplifiers with outputs that are duo-directional depending on the signal sense; the commonly-used push-pull arrangements are examined, analytically and experimentally, for auto-self-excited transductor pairs. The theoretical and practical performance of the arrangements are compared, and guidance is given on suitable design proportions.

DOI:10.1049/pi-2.1954.0135

出版商:IEE    

年代:1954

数据来源: IET

摘要:

It is shown that, whereas the m.m.f. gain of a transductor without self-excitation is almost independent of the properties of the core, that for a transductor with 100% self-excitation is determined to a large extent by the shape of the magnetization curve of the core material. By combining in one core materials of different properties, it has been found possible to produce a relatively inexpensive core suitable for use in instrument transductors.

DOI:10.1049/pi-2.1954.0136

出版商:IEE    

年代:1954

数据来源: IET

DOI:10.1049/pi-2.1954.0139

出版商:IEE    

年代:1954

数据来源: IET

DOI:10.1049/pi-2.1954.0140

出版商:IEE    

年代:1954

数据来源: IET

DOI:10.1049/pi-2.1954.0141

出版商:IEE    

年代:1954

数据来源: IET