摘要:

The paper deals primarily with a new development in methods of producing lead cable-sheaths, in which the pressure required to extrude the lead is obtained by means of a motordriven screw member instead of by the ram of a hydraulic press which has hitherto been universal practice. The author's experiments were commenced in 1929 when the first lead pipe was extruded by a continuous process, and the development has continued steadily up to the present day, and to the stage where commercial continuous lead-extrusion machines are now being delivered. After reviewing in detail the disadvantages of former methods in order to explain the reasons for the development, the paper describes the construction and operation of the continuous lead-extrusion machine, and from considerations of the physical and metallurgical properties of the sheath demonstrates the improvements in the product achieved. As the advantages attendant on the use of the continuous lead-extrusion machine are associated to some extent with the methods employed in melting the lead, and in the handling of the cable as it comes from the machine, special attention has been given to these features alongside the development of the machine itself. The paper describes improved lead handling and melting equipment and automatic reeling mechanism for he finished cable.

DOI:10.1049/jiee-1.1937.0054

出版商:IEE    

年代:1937

数据来源: IET

摘要:

It is pointed out that, although dielectric losses in certain materials are frequently attributed to the presence of particles of conducting impurity, any discussion as to the type and magnitude of loss produced by a given quantity and disposition of impurity is often extremely vague or entirely lacking. A description is given of some experiments with a suspension of water droplets in wax, the results of which did not agree with the predictions of Wagner's theory except when the suspension was kept at a temperature near to the melting point of the wax. The behaviour of a model inhomogeneous material containing spheroidal particles is investigated analytically and it is concluded that a minute amount of conducting impurity in the form of fine needles could produce a serious loss at low frequencies, although the effect of the same quantity of impurity in spherical form would be negligible.

DOI:10.1049/jiee-1.1937.0058

出版商:IEE    

年代:1937

数据来源: IET

摘要:

A method is outlined of designing single-phase conductors with small eddy-current losses. Experimental results are given verifying the theory and the accuracy of the formula for calculating the eddy-current losses.

DOI:10.1049/jiee-1.1937.0059

出版商:IEE    

年代:1937

数据来源: IET

摘要:

The authors discuss the main features in the geometrical design of the types of valve in common use to-day and the various factors, mechanical and chemical, which impose limitations in manufacture. The minimum tolerances to which it is possible to reproduce characteristics are indicated. The paper includes a brief historical survey of the recent improvements in thermionic emitters and gives details of the precautions necessary in the production of modern highly efficient oxide-coated cathodes and insulated heaters. Pumping and activation processes are described, and the main factors affecting the life of a valve are discussed. The last section of the paper deals with some of the limitations encountered in the use of valves, such as hum, microphony, noise, and frequency limitation, and the methods of minimizing these factors are given. The authors conclude with some observations on possible future developments.

DOI:10.1049/jiee-1.1937.0060

出版商:IEE    

年代:1937

数据来源: IET

摘要:

The paper describes an attempt to determine experimentally the accuracy of Butterworth's formulae for the highfrequency resistance of single-layer solenoids. The investigation has been carried out on 4-in. diameter air-spaced coils of 10, 30, and 50 turns over the frequency range from 2 × 105to 2.025 × 106cycles per sec. The coils were wound with bare wire of diameter 1.63 mm. (No. 16 S.W.G.), with a distance of'2.60 mm. between the centres of adjacent wires. The method of measurement described was based on the use, for each coil shape, of a series of identical coils wound with copper, aluminium, brass, german silver, and eureka wire, respectively. There is some uncertainty in the interpretation of the results, but, in spite of this, it is evident that of the two formulae with which a comparison is made, one of them is correct to within about 4 per cent for the 30- and 50-turn coils over the whole frequency range considered. This formula is quite inapplicable to the 10-turn coils; however, for these the second formula gives reasonably good agreement with the experimental results.

DOI:10.1049/jiee-1.1937.0062

出版商:IEE    

年代:1937

数据来源: IET