Recent Progress in Dynamo-electric Machines: Being a Suppplement to "Dynamo-electric Machinery."

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D. Van Nostrand, 1884 - 113 Seiten
 

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Seite 101 - He had always found theoretical men rather inclined to look with a certain amount of disdain upon practical men, and to think that practical men knew nothing about their subject unless they followed the dictates of theorists.
Seite 56 - Gramme rings upon one axle, which lies between the poles of two opposing field-magnets, each of the two branched, or so-called horse-shoe form. These are laid horizontally, so that the north pole of one is opposite the south pole of the other, and vice versa, the poles being provided with curved polepieces between which the rings revolve. M. Deprez, who has given much attention to the question how to design a machine which, with the least expenditure of electric energy, gives the greatest actual...
Seite 59 - ... has devoted attention to the winding of the field-magnets, so as to secure a constant potential at the terminals. After experimenting with various methods of compounding, he finds that the best results are arrived at in the following way : In his four-pole dynamo there are eight cores to be wound. Each of these receives a shunt coil of fine wire, and outside this a main coil of stout wire. The eight fine wire coils are then joined up in series with one another, and connected as a shunt to the...
Seite 23 - He finds that the complicated mathematical expression for this case, when examined, shows negative values for angles between 12° and 90°. The curves of values that satisfy his equations have minima exactly in those regions where his experiments revealed them. This is very satisfactory as far as it goes. But we .may deduce a precisely similar conclusion in a much simpler manner, from considering the form and distribution of the lines of magnetic force in the field. These are shewn in Fig.
Seite 63 - DYNAMO (4-PoLE). special pains to ensure that there are no electric circuits made in the bolting together of these cores, each plate being both electrically and magnetically insulated from the adjacent plates. Eddy currents in the core are thus almost entirely obviated. This was far from being the case with some of the earlier machines, in which, as in the Edison machine until Dr. Hopkinson improved it, the bolts holding together the cores constituted an available path for wasteful inductions.
Seite 22 - Two questions naturally arise: Why should such detrimental inductions arise in the ring ? and how can they be obviated? The researches of Dr. Isenbeck supply the answer to both points. Dr. Isenbeck has calculated from the laws of magnetic potential the number of lines of force that will be cut at the various points of the path of the ring. He finds that the complicated mathematical expression for this case, when examined, shows negative values for angles between 12° and 90°.
Seite 17 - ... with a galvanometer. On vibrating it isochronously with the swing of the needle of the galvanometer, the latter is set in motion by the induced currents, and the deflexion which results shows the relative amount of induction going on in the particular part of the field where the coil is situated. The vibrations of the frame are limited by stocks to an angle of 7° 5'.

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