CHAPTER YII.

Regulator for Rotary Current Motors.

An interesting device for regulating and reversing has beendevised by Mr. Tesla for the purpose of varying the speed ofpolyphase motors. It consists of a form of converter or trans-former with one element capable of movement with respect tothe other, whereby the inductive relations may be altered, eithermanually or automatically, for the purpose of varying thestrength of the induced current. Mr. Tesla prefers to constructthis device in such manner that the induced or secondary ele-ment may be movable with respect to the other ; and the inven-tion, so far as relates merely to the construction of the device it-self, consists, essentially, in the combination, with two oppositemagnetic poles, of an armature wound with an insulated coil andmounted on a shaft, whereby it may be turned to the desiredextent within the held produced by the poles. The normal po-sition of the core of the secondary element is that in which itmost completely closes the magnetic circuit between the polesof the primary element, and in this position its coil is in itsmost effective position for the inductive action upon it of theprimary coils; but by turning the movable core to either side,the induced currents delivered by its coil become weaker until,by a movement of the said core and coil through 90°, there willbe no current delivered.

Fig. 34 is a view in side elevation of the regulator. Fig. 35 isa broken section on line x x of Fig. 34. Fig. 36 is a diagramillustrating the most convenient manner of applying the regulatorto ordinary forms of motors, and Fig. 37 is a similar diagram illus-trating the application of the device to the Tesla alternating-current motors. The regulator may be constructed in manyways to secure the desired result; but that which is, perhaps, itsbest form is shown in Figs. 34 and 35.

a represents a frame of iron, b b are the cores of the indue-