POLTPHASE CURRENTS.
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alternating-current generator with, say, two poles, m m', .and anarmature wound with two coils, u n', at right- angles and con-nected in series. The motor lias, for example, four poles woundwith coils b c, which are connected in series, and an armaturewith polar projections d wound with closed coils e e. From thecommon joint or union between the two circuits of both the gen-erator and the motor an earth connection is established, whilethe terminals or ends of these circuits are connected to theline. Assuming that the motor is a synchronizing motor or onethat has the capability of running in synchronism with the gen-erator, but not of starting, it may be started by the above-described apparatus by closing the ground connection from botligenerator and motor. The system thus becomes one with a two-circuit generator and motor, the ground forming a common re-turn for the currents in the two circuits l and l '. When bythis arrangement of circuits the motor is brought to speed, theground connection is broken between the motor or generator, orboth, ground-switches pp' being employed for this purpose.The motor then runs as a synchronizing motor.
In describing the main features which constitute this inventionillustrations have necessarily been omitted of the appliances usedin conjunction with the electrical devices of similar systems—such, for instance, as driving-belts, fixed and loose pulleys for themotor, and the like; but these are matters well understood.
Mr. Tesla believes he is the first to operate electro-magneticmotors by alternating currents in any of the ways herein described—that is to say, by producing a progressive movement or rota-tion of their poles or points of greatest magnetic attraction bythe alternating currents until they have reached a given speed,and then by the same currents producing a simple alternation oftheir poles, or, in other words, by a change in the order or char-acter of the circuit connections to convert a motor operating onone principle to one operating on another.