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CHAPTEK IV.

Modifications and Expansions of the Tesla Polyphase

Systems.

In his earlier papers and patents relative to polyphase currents,Mr. Tesla devoted himself chiefly to an enunciation of the broadlines and ideas lying at the basis of this new work; but he sup-plemented this immediately by a series of other striking inven-tions which may be regarded as modifications and expansions ofcertain features of the Tesla systems. These we shall now pro-ceed to deal with.

In the preceding chapters we have thus shown and describedthe Tesla electrical systems for the transmission of power and theconversion and distribution of electrical energy, in which themotors and the transformers contain two or more coils or sets ofcoils, which were connected up in independent circuits wfithcorresponding coils of an alternating current generator, the opera-tion of the system being brought about by the co-operation ofthe alternating currents in the independent circuits in progres-sively moving or shifting the poles or points of maximum mag-netic effect of the motors or converters. In these systems twoindependent conductors are employed for each of the independ-ent circuits connecting the generator with the devices for con-verting the transmitted currents into mechanical energy or intoelectric currents of another character. This, however, is notalways necessary. The two or more circuits may have a singlereturn path or wire in common, with a loss, if any, which is soextremely slight that it may be disregarded entirely. For thesake of illustration, if the generator have two independent coilsand the motor two coils or two sets of coils in corresponding rela-tions to its operative elements one terminal of each generatorcoil is connected to the corresponding terminals of the motorcoils through two independent conductors, while the oppositeterminals of the respective coils are both connected to onereturn wire. The following description deals with the modifica-