摘要:

The paper sets forth the results of a number of mathematical investigations into the behaviour of electric winders during the periods of acceleration and retardation.The starting and stopping conditions both of Ward Leonard and of induction-motor-driven winders are examined with a particular view to finding out how nearly the conventional calculated speed, torque and input diagrams can be approached in practice, and the causes of departure therefrom.The possible types of acceleration and retardation that can be set up are used as a basis for examining rope stresses. Relative rope stresses are compared as between Ward Leonard and induction-motordriven winders, and as between winders working at low speeds with heavy loads and those working at high speeds with light loads.Only those starting and stopping conditions have been examined in which the variation of the controlling resistors, or currents, is an independent function of time.

DOI:10.1049/pi-2.1951.0156

出版商:IEE    

年代:1951

数据来源: IET

摘要:

In many parts of the world where the load density is low and major loads and generation are 200–300 miles apart, voltage control is costly if constant-voltage transmission is used. Such systems are usually radial, and generally considerable development, spread over many years, will have to take place before the interconnections of generating stations result in the familiar grid.Consideration is given in the paper to the effects of using variable-voltage generators on such radial systems. It is shown that if, at times of light load, the generation voltage is reduced to, for example, 90%, and at times of full load it is increased to, for example, 110%, a considerable reduction in synchronous condenser capacity is possible.Such systems are also characterized by small loads tapped off the main transmission, and an example is given of such a system. This shows that, with synchronous condensers at the major terminal load, if the receiver secondary voltage is kept constant and the generation voltage is varied linearly with power, the voltage at the intermediate loads will be reasonable, even if the main load is lost.

DOI:10.1049/pi-2.1951.0161

出版商:IEE    

年代:1951

数据来源: IET

摘要:

Up to the present time, process controllers have been pneumatic; the paper describes an electronically operated controller.Brief statements on the fundamental principles of process controlare given, and these lead to the mathematical equation which any process controller must solve.The basic principles of one method of converting the physical quantities to be measured into direct current are described; this method permits the use of a controller of a purely electronic type. The circuit arrangements of the controller which solves the fundamental equation are given in detail. The d.c. output from the controller is used to position the orthodox pneumatically operated process-control valve by means of an electro-pneumatic relay mounted on the valve.Some of the advantages claimed for the use of an electrical method as against others are listed.The method of operating the controller when installed on a plant is described, and details are given of an electronic process analogue used for testing the controller.

DOI:10.1049/pi-2.1951.0164

出版商:IEE    

年代:1951

数据来源: IET

摘要:

A power stroboscope has been developed for high-speed flash photography at picture repetition rates from 100–4000 pictures/sec, the duration of each flash being 5 microsec. The control circuit uses a hydrogen thyratron to trigger the tube discharge, and the energy is supplied to the lamp at 12 kV. The storage capacitor of 0.1 μF delivers 4 joules to the lamp.During the development it was found that the light emission from a low-pressure xenon-filled tube persisted for a considerable time after current had ceased to flow. This afterglow in xenon discharges is greatly reduced by an increase in gas pressure and other changes in the physical design of the lamp.The stroboscope can be used for direct photography with a drum camera, or it can be synchronized with the optical compensation element of an image-compensated camera.Some examples of the application of the system to cavitation research are given.

DOI:10.1049/pi-2.1951.0167

出版商:IEE    

年代:1951

数据来源: IET

摘要:

An image convertor has been used as a shutter mechanism for exposure durations of less than 1 microsec. The electron emission from the photo-cathode is controlled by suitable electrode potentials and the fluorescent image formed during the exposure interval is recorded photographically. The characteristics of two types of image convertor are discussed, distortions which are peculiar to short exposure conditions are observed and an explanatory mechanism is suggested.The use of magnetic image deflection, whereby a line image may be given a deflection which varies with time, is also described, and streak records showing the variations in the object (along one dimension) as a function of time are discussed.

DOI:10.1049/pi-2.1951.0171

出版商:IEE    

年代:1951

数据来源: IET

DOI:10.1049/pi-2.1951.0178

出版商:IEE    

年代:1951

数据来源: IET

DOI:10.1049/pi-2.1951.0179

出版商:IEE    

年代:1951

数据来源: IET

DOI:10.1049/pi-2.1951.0180

出版商:IEE    

年代:1951

数据来源: IET

DOI:10.1049/pi-2.1951.0181

出版商:IEE    

年代:1951

数据来源: IET