[Electric engineering.] . Fig. 21. runs through a block of wood h, thus confining the arcand preventing it from arcing and burning the terminals t, 21 {b) shows the box closed and in the position in whichit is placed on the pole. In the General Electric single-poleprimary cut-out, the wires enter at the bottom, as shown in J. III.—5 60 ELECTRIC TRANSMISSION. 14 Fig. 19. Where large transformers are operated in substa-tions, automatic switches or circuit-breakers are used insteadof fuses to disconnect the transformer from the line in caseof a short circuit or overload. TRANSFORMERS ON SI
[Electric engineering.] . Fig. 21. runs through a block of wood h, thus confining the arcand preventing it from arcing and burning the terminals t, 21 {b) shows the box closed and in the position in whichit is placed on the pole. In the General Electric single-poleprimary cut-out, the wires enter at the bottom, as shown in J. III.—5 60 ELECTRIC TRANSMISSION. 14 Fig. 19. Where large transformers are operated in substa-tions, automatic switches or circuit-breakers are used insteadof fuses to disconnect the transformer from the line in caseof a short circuit or overload. TRANSFORMERS ON SINGLE-PHASE CIRCUITS. 74. Transformers in Parallel.—Transformers may beconnected in parallel so as to feed a single circuit, as shown ? in Fig. 22, but care 2000 Vo/fs1. must be taken in con-~^T 3~ meeting them up, or else [}— Fuses —\j Q.— Fuses —>\\ a short circuit may re-sult. We will supposethat the two transform-ers to be connected inparallel are of the sametype, so that they willboth be wound primary terminalsPx and P% must be con-nected to the samemain, and P„ and P4 to the other main. If this is done,then the secondary terminals a and c, and b and d will havethe same polarity at the same instant, and these terminalsshould be connected together, as shown. The external cir-cuit, consisting of lamps or other load, is connected to thesecondary mains. Now, it will be noticed that, from theway in which the two secondaries are connected, they opposeeach other, and that little or no current will flow until theoutside circuit is connected. In practice, it will be foundthat a small current will flow between the transformers, current will not be at all large. Suppose, however,that the secondary terminals should be connecte
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