摘要:

The induction-type synchronous motor is a polyphase motor and has a cylindrical rotor. It is started as an induction motor of the slip-ring type and synchronizes itself when direct current is switched into the rotor.The characteristics and construction of this type of motor are compared with those of other polyphase motors.The self-synchronizing feature of this type of machine is discussed in detail so as to present a full physical conception of the phenomena which occur, and the subject is illustrated by means of oscillograms.A mathematical expression is deduced for the limiting conditions beyond which synchronizing is uncertain.The considerations which determine the selection of the excitation voltage are discussed, as well as the method of control and other practical points affecting the installation of these machines.

DOI:10.1049/jiee-1.1922.0005

出版商:IEE    

年代:1922

数据来源: IET

摘要:

The paper has for its object the more definite determination of the constants of the liquid rheostat, and the more exact prediction of its performance.First, the phenomena occurring in such a rheostat under a wide variety of circumstances are considered, a distinction being drawn between the behaviour of direct and of alternating currents in the apparatus. Tests are described which bear out and amplify the conclusions, many of which are characterized by the employment, with impunity, of current densities many times larger than those generally considered to fall within the limits of safety.Representative designs of rheostats, for both small and large horse-powers, are described and criticized.A mathematical method is developed for conveniently arriving at the capacity of a given liquid starter, from thermal considerations, which form the deciding factor in this case. A more elaborate calculation is also given, capable of more general application.The effecting of artificial cooling for liquid controllers is dealt with, descriptions of the pipe-cooled and the adjustable weir types being included.The functions of a liquid slip-regulator are analysed and the usual pattern is reviewed, the conclusion being reached that it could be simplified with considerable advantage.Finally, suggestions are made with regard to specifications for governing the design and construction of this apparatus.

DOI:10.1049/jiee-1.1922.0007

出版商:IEE    

年代:1922

数据来源: IET

摘要:

Of the three principal constituents of electrical machinery the greatest improvements in the future are to be looked for in the insulating materials. A knowledge of the effect of heat upon the electrical and mechanical characteristics of insulating materials is of the greatest practical importance. An investigation has been carried out to ascertain the variation in electric strength between temperatures of 30° C. and 100° C. of many of the solid insulating materials at present employed in the manufacture of electrical machinery and apparatus. These tests show that in the case of some of the materials used at present the breakdown voltage at 100° C. may be only one-half that at 30° C. Except in the case of certain mica products the electric strength of all the materials was found to decrease appreciably with increase in temperature. Consequently, all insulating materials should be judged and used in accordance with the breakdown voltage at 100° C. and not on the results of tests carried out at air temperature. Further research work would appear desirable: (a) to investigate other materials on the lines of these tests, and also the effect of heat on the mechanical properties; and (b) to develop new insulating materials with better electrical and mechanical properties at temperatures likely to be attained in modern electrical machinery.

DOI:10.1049/jiee-1.1922.0009

出版商:IEE    

年代:1922

数据来源: IET

摘要:

This paper consists in the main of a record of experimental progress directed towards the mechanicalization of wireless telegraphy in as simple and portable a form as possible.One of the great difficulties in a modern war on a large scale was shown to be that of providing at short notice the trained personnel necessary for the manipulation of scientific and highly technical apparatus. Simplicity in handling such apparatus is therefore a matter of great importance.Experimental work has now arrived at a point at which it has been shown by practical experience that apparatus can be produced which, in the hands of operators of average ability, enables wireless telegraphy to be carried on by mechanical operations both in transmission and in reception, either by itself or in continuation of a line system; and this at all speeds up to the maximum of Wheatstone apparatus.

DOI:10.1049/jiee-1.1922.0011

出版商:IEE    

年代:1922

数据来源: IET