CHAPTER XXIII.
Tesla Polyphase Tkanseokmek.
Applying- tlie polyphase principle to the construction of trans-formers as well to the motors already noticed, Mr. Tesla has in-vented some very interesting forms, which lie considers freefrom the defects of earlier and, at present, more familiar forms.In these transformers he provides a series of inducing coils andcorresponding induced coils, which are generally wound upon acore closed upon itself, usually a ring of laminated iron.
The two sets of coils are wound side hy side or superposed orotherwise placed in well-known ways to bring them into the mosteffective relations to one another and to the core. The inducingor primary coils wound on the core are divided into pairs or setsby the proper electrical connections, so that while the coils ofone pair or set co-operate in fixing the magnetic poles of thecore at two given diametrically opposite points, the coils of theother pair or set—assuming, for sake of illustration, that thereare but two—tend to lix the poles ninety degrees from suchpoints. With this induction device is used an alternating currentgenerator with coils or sets of coils to correspond with those ofthe converter, and the corresponding coils of the generator andconverter are then connected up in independent circuits. It re-sults from this that the different electrical phases in the genera-tor are attended hy corresponding magnetic changes in the con-verter; or, in other words, that as the generator coils revolve,the points of greatest magnetic intensity in the converter will beprogressively shifted or whirled around.
Fig. 92 is a diagrammatic illustration of the converter and theelectrical connections of the same. Fig. 9?> is a horizontal cen-tral cross-section of Fig. 92. Fig. 94 is a diagram of the circuitsof the entire system, the generator being shown in section.
Mr. Tesla uses a core, a, which is closed upon itself—that is tosay, of an annular cylindrical or equivalent form—and as theefficiency of the apparatus is largely increased by the subdivision