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

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D. Van Nostrand, 1892 - 113 Seiten
 

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Seite 97 - 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 - ... 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 couple at the axle, is of opinion that the horse-shoe form of electro-magnet is the most advantageous.
Seite 49 - Edison machines were made of thin iron discs, separated by paper slipped on over a sleeve of lignum vitoe, and held together by six longitudinal bolts passing through holes in the core-plates, and secured by nuts to end- plates. These bolts are now removed, and the plates are held together by great washers, running upon screws cut on the axle of the armature. The size of the central hole in the plates has been diminished, thus getting into the interior more iron, and providing a greater cross-section...
Seite 17 - ... center, is carried a ring of wood or iron, upon which is placed at one point a small coil of fine wire. This corresponds to a single section of the coils of a Pacinotti or of a Gramme ring, of which the ring of wood or iron constitutes the core. The coil can be adjusted to any desired position on the ring, and the ends communicate 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...
Seite 23 - He finds that the complicated mathematical expression for this case, when examined, shows negativo 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 shown in fig. 7, together...
Seite 59 - In particular, he 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...
Seite 63 - ... 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...
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 84 - ... which, therefore, can be brought very close to the surface of the rotating cylinder. Amongst other improvements, also, segments of the collector are internally cross-connected, so that only two brushes are needed instead of six as formerly. Several improvements in mechanical details...

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