摘要:

A description is given of the high-voltage X-ray tube and one-million-volt d.c. generator installed in the Mozelle Sassoon X-ray Therapy Department of St. Bartholomew's Hospital. The building contains a treatment room located between two generator rooms. The central portion of the X-ray tube, from which the X-ray beam emerges, traverses the treatment room and projects into each generator room. The generator rooms each house 500-kV d.c. generators. The X-ray tube and thermionic rectifiers used in the d.c. generators are evacuated continuously by oil diffusion pumps, and the whole apparatus is readily demountable. Removable filament assemblies are fitted to the rectifiers and facilitate rapid replacement of filaments; and a special cathode with 6 interchangeable filaments has been developed for the X-ray tube to avoid frequent admission of air into the tube during filament replacements. The tube is now used continuously at 1 000 kV and has been operated experimentally at 1 100 kV. Several structural changes have been, made for reasons stated later, and the performance of the tube is fully described. Curves relating X-ray output with voltage and filtration by metallic niters are given, and a radiograph as included to illustrate the capabilities of the tube if applied to industrial radiography. Comparisons are made between this tube and high-voltage tubes operating in other parts of the world.

DOI:10.1049/jiee-1.1939.0227

出版商:IEE    

年代:1939

数据来源: IET

DOI:10.1049/jiee-1.1939.0232

出版商:IEE    

年代:1939

数据来源: IET

摘要:

Modern telephone systems utilize extensive networks of bare lead-sheathed cables drawn into earthenware conduit. As with other underground structures, the cable sheaths are liable to corrosion. In the absence of electrolytic stimulation the rate at which this takes place depends more on the nature of the soil waters, etc., than on the composition of the sheathing material. The danger is increased by the electrolytic action of stray currents passing between the sheath and its environment by ionic paths. Such currents may be the result of leakage from electric traction systems with uninsulated return, or may arise from the setting-up of primary-cell actions due to inhomogeneities in the environment of the cable.Laboratory examination of samples of corroded sheathing, together with chemical analysis of the corrosion products and soil waters, enable definite conclusions to be reached as to whether there has been electrolytic stimulation. In general; this produces a pitted surface, an intercrystalline type of attack and, with normal soil waters, a corrosion product rich in chloride. The actual field measurement of the intensity of the current discharge from the sheath in the dangerous anodic areas does not yet appear possible. Useful information has, however, been obtained from apparatus recording the sheath current at two points a short distance apart. Increasing use is also being made of standard “half-cell” electrodes for the accurate determination of the small potential differences existing between a sheath and its immediate surroundings.Electrical drainage has been used extensively abroad for the protection of cable sheaths in the stray-current fields of electric tramways. In Italy this method has been used with shunted insulating gaps in the cable sheaths in such a way that there is no increased danger to other buried pipe systems. The British Post Office has been successful in obtaining protection solely by the planned insertion of numerous insulating gaps in a cable system. Protective coverings are in use, although they make the pulling of cables into and outlof cable ducts more difficult. It has been found, however, that the chemical attack of corrosive soil waters may be retarded by the addition of a chemical inhibitor to the lubricant used when the cable is first drawn in.

DOI:10.1049/jiee-1.1939.0233

出版商:IEE    

年代:1939

数据来源: IET

摘要:

The paper is brief description of a system devised by the author to exercise control over the rate of acceleration and deceleration of Ward-Leonard and Ward-Leonard-Ilgner mine winders by purely electrical means, irrespective of the position of the driver's control lever. It also describes how the system is used for controlled regenerative braking in embergency. The paper consists of the following parts:-(1) A description of the control exciter, with the method of field mixing used to provide the required output characteristic.(2) A description of the field control resistance used to vary the characteristic according to the position of the cages in the shaft.(3) The application of the control exciter in normal service.(4) The application of the control exciter in emergency conditions.(6) Results obtained.

DOI:10.1049/jiee-1.1939.0235

出版商:IEE    

年代:1939

数据来源: IET

摘要:

It has been realized for some time that fire risk in electrical installations involves special consideration owing to the nature of the combustible materials involved. Preliminary study of the problem resulted in the risks being divided into four categories, and a series of tests was undertaken with varying available media and different installations in each category. This paper describes briefly the test installations designed and erected for this purpose and gives a general outline of the testing technique involved. Tables are given showing the results of the tests, with explanatory notes where necessary for each test. The paper concludes with a discussion of the test results, and general recommendations are given in regard to the various categories of risk tested.

DOI:10.1049/jiee-1.1939.0236

出版商:IEE    

年代:1939

数据来源: IET

DOI:10.1049/jiee-1.1939.0247

出版商:IEE    

年代:1939

数据来源: IET