IdAGNET'O-ELECTRIC MACHINE (More recent forms of). Of late years, quite a nor era has arisen in the construction of mag neto-electric machines. The compactness. simplicity of construction, and marvelous power which the new machines possess, give them quite a novel importance in practical electricity. The names chiefly associated with the new improvements are -Wilde of Manchester, Siemens and Wheat stone, and Gramme of Paris. Mr. H. Wilde, in 1866, patented a magneto-elec tric machine, founded on the principle that a current Or a magnet indefinitely weak can be made to induce a current or a magnet of indefinite strength. A general description will show how this is proved and applied.
Wilde's original machine is shown in front elevation, fig. 1. It consists of two machines very shnilar to each other, the upper one M M', and the lower E E'. The upper and smaller machine consists of 16 permanent magnets, placed one behind the other. The front one only is seen. The poles of these are fixed at g, g (fig. 2), to what is termed the magnet cylinder. This consists of a hollow tube, made up of heavy- masses of cast-iron, c, c, at each side, separated from each other by brass rods, b, the whole being knit firmly gether, above and below, by brass bolts at r, r'. The cast-iron side pieces thus form the poles of the magnetic battery. The armature, which revolves within the tube of the magnet cylinder, is a long piece of soft iron, a a, and in section resembles an " II." In the hollows of the " H" the wire is turned longitudinally. This armature is shown separately in fig. 3, part of the wooden tops which cover in the wire being removed to show how the wire is turned. This form of armature was first constructed by Siemens. The ends of the armature wire are soldered to two insulated iron rings, n, n' (fig. 3), against which the springs, s,s (fig. 1), press, which convey the current from the revolving armature; TA is the pulley of the driving-belt. If the cross bar of the "H" stand upright (it lies horizon tally in the figure), and the armature be turned round, while wires leading from the binding-screws, r, r' (fig.1), are connected with a galvanometer, it will be found that the current induced by the motion is in the same direction till thecross is again upright, but inverted. If the motion be continued beyond that point, a current in the opposite direction will ensue, lasting till the cress-bar is in its first position. The right half of the armature givec off always one kind of electricity, and the left the other. The right and left springs, s, s, are thus always like poles, for they change from n to n' (fig. 3) when the current in the armature changes. We come novr to describe the singular peculiarity and merit of Wilde's machine. The current got from the magneto-electric machine is not directly made use of, but is employed to generate an electro magnet some hundreds of times more powerful than the magnetic battery originally employed, by means of which a corresponding increase of electricity may be obtained. This electro-mag
net, E E' (fig. 1), forms the lower part of the figure, and by far the most bulky portion of the entire machine. It is of the horse-shoe form, E and E' forming the two limbs of it. The core of each of these, shown by the dotted lines, is formed by a plate of rolled iron, 36 in. in height, 26 in. in length, and 1 in. in thickness. Each is surrounded by a coil of insulated cop per wire (No. 10), 1650 ft. long, wound round lengthwise in 7 layers. The current bas thus, in passing from the insulated binding-screw r to the similar screw r', to make a circuit of 3,300 feet. Each limb of the electro-magnet is thus a flat reel of covered wire wrapped round a sheet of iron, the rounded ends alone of which arc seen in the figure.
The upright iron plates are joined above by a brid,ge, P, built up also of iron-plate, and are fixed below the whole way along. with the iron bars v, v to the sides of a magnet-cylinder of precisely the same construction as the one already described. Tile iron frame-work of the electro-magnet is shown by the dotted lines. The depth of the bridge is the same as the breadth of the bars v', which are of the same size as the bars v, v. The various surfaces of juncture in the frame-work are planed, so as to insure perfect metallic contact. The upper and lower machine are in action precisely alike, only the upper magnet is a per manent magnet, and the lower one an electro-magnet. We have the same magnet-cylinder, I, I, the same armature, A, and springs, S, S', and the same poles, Z, Z'; the size is, however, different; the caliber of the macmet-cylinder is 7 inches. The diameter of the lower arma ture giveAlie name to the machine—viz. a 7-inch machine. Figs. 2 and 3 are on the scale of the lower machine (fig. 1). The length of wire on the lower armature is 330 feet. It is 35 in. in length, and is made to rotate 1800 times a minute. The cross frame-work attached at g g to the magnet-cylinder, in which the front journal, f, of the armature rotates (at Q), is shown in the lower machine (fig. 1). 1Vhen the machine is in action, both armatures are driven shnultaneously by belts from the same countershaft. For the electric light, the cur rents conveyed to the springs, S and S', need not be sent in the same direction. In that case, the separation between n and n' is vertical; and each spring presses against only one ring during the whole revolu tion, receiving and transmitting each revolution two opposite cur rents. Oil for the journal and commutator is supplied from the cup C.