440

INVENTIONS OF NIKOLA TESLA.

rent will flow over tlie auxiliary brush in an opposite direction,and the current in m will be strengthened, and in m' partly neu-tralized.

By combining with the brushes a , h , and o any usual automaticregulating mechanism, the current developed can be regulated inproportion to the demands in the working circuit. The parts m

Fig. 254.

and m' of the field wire may be wound in the same direction.In this case they are arranged as shown in Fig. 253 ; or the partm may be wound in the opposite direction, as shown in Figs.

254 and 255.

It will be apparent that the respective cores of the field-mag-nets are subjected to neutralizing or intensifying effects of thecurrent in the shunt through c', and the magnetism of the coreswill be partially neutralized, or the points of greatest magnetismshifted, so that it will be more or less remote from or approach-ing to the armature, and hence the aggregate energizing actionsof the field magnets on the armature will be correspondinglyvai'ied.

In the form indicated in Fig. 253 the regulation is effected byshifting the point of greatest magnetism, and in Figs. 254 and

255 the same effect is produced by the action of the current inthe shunt passing through the neutralizing helix.

The relative positions of the respective brushes may be variedby moving the auxiliary brush, or the brush o may remain station-ary and the core p be connected to the main-brush holder a,so as to adjust the brushes a b in their relation to the brush c.If, however, an adjustment is applied to all the brushes, as seenin Fig. 257, the solenoid should be connected to both a and c, soas to move them toward or away from each other.

There are several known devices for giving motion in propor-