74

INVENTIONS OE NIKOLA TESLA.

tie current to pass. On the other hand, no such opposition beingencountered in the other set of coils, the current passes freelythrough them, magnetizing the poles on which they are wound.As soon, however, as the laminated bridges become saturatedand incapable of carrying all the lines of force which the risingelectromotive force, and consequently increased current, pro-duce, free poles are developed at the ends of the cores, which,acting in conjunction with the others, produce rotation of thearmature.

The construction in detail by which this invention is illustratedis shown in the accompanying drawings.

Fig. 60 is a view in side elevation of a motor embodying theprinciple. Fig. 61 is a vertical cross-section of the motor, a isthe frame of the motor, which should be built up of sheets ofiron punched out to the desired shape and bolted together with

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Fig. 61

Fig. 60.

mmBSk

insulation between the sheets. When complete, the frame makesa tield-magnet with inwardly projecting pole-pieces b and c. Toadapt them to the requirements of this particular case these pole-pieces are out of line with one another, those marked b surround-ing one end of the armature and the others, as c, the oppositeend, and they are disposed alternately—that is to say, the pole-pieces of one set occur in line with the spaces between those of theother sets.

The armature d is of cylindrical form, and is also laminated inthe usual way and is wound longitudinally with coils closed uponthemselves. The pole-pieces c are connected or shunted bybridge-pieces e. These may be made independently and attachedto the pole-pieces, or they may be parts of the forms or blanksstamped or punched out of sheet-iron. Their size or mass is de-