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INVENTIONS OF NIKOLA TESLA.

In Fig. 28, let c represent a cylindrical armature core woundlongitudinally with insulated coils a a, which are connected upin series, the terminals of the series being connected to collecting-rings a a on the shaft g. By means of this shaft the armatureis mounted to rotate between the poles of an annular field-mag-net i), formed with polar projections wound with coils e, thatmagnetize the said projections. The coils e are included in thecircuit of a generator r, by means of which the field-magnet isenergized. If thus constricted, the machine is a well-knownform of alternating-current generator. To adapt it to his sys-tem, however, Mr. Tesla winds on armature c a second set ofcoils b b intermediate to the first, or, in other words, in such po-sitions that while the coils of one set are in the relative positionsto the poles of the field-magnet to produce the maximum current,those of the other set will be in the position in which they pro-duce the minimum current. The coils b are connected, also, in

MIS

Fig. 30.

Fra. 31.

series and to two connecting-rings, secured generally to theshaft at the opposite end of the armature.

The motor shown in Fig. 29 has an annular field-magnet h,with four pole-pieces wound with coils i. The armature is con-structed similarly to the generator, but. with two sets of twocoils in closed circuits to correspond with the reduced number ofmagnetic poles in the field. From the foregoing it is evident thatone revolution of the armature of the generator producing eightcurrent impulses in each circuit will pi'oduce two revolutions ofthe motor-armature.

The application of the principle of this invention is not, how-ever, confined to any particular form of machine. In Figs. 30and 31 a generator and motor of another well-known type areshown. In Fig. 30, j j are magnets disposed in a circle andwound with coils k, which are in circuit with a generator which