[Electric engineering.] . ransformers devisedby. Mr. C. F. 32 shows the con-nections necessary. Twotransformers A and Bhave their primary coils Pand P connected to thetwo-phase mains asshown. The secondary vSof transformer y^ has .87times as many turns asthe secondary S of trans-former B. One end of S is connected to the middle point cof S. The three-phase lines are attached to terminals e, b, scheme of transformation is used quite largely atNiagara, where two-phase generators are used and the cur-rent transformed to three-phase for transmission to Buffalo. 83. Capacity of Tr
[Electric engineering.] . ransformers devisedby. Mr. C. F. 32 shows the con-nections necessary. Twotransformers A and Bhave their primary coils Pand P connected to thetwo-phase mains asshown. The secondary vSof transformer y^ has .87times as many turns asthe secondary S of trans-former B. One end of S is connected to the middle point cof S. The three-phase lines are attached to terminals e, b, scheme of transformation is used quite largely atNiagara, where two-phase generators are used and the cur-rent transformed to three-phase for transmission to Buffalo. 83. Capacity of Transformers on Two- and Three-Phase Systems.—When transformers are connected on atwo-phase system, as, for example, to feed a two-phasemotor, each transformer has to be of capacity sufficient tocarry half the load. If the three-phase system using threetransformers is used, each transformer must be capable ofcarrying one-third the load. When the transformers areused to operate induction motors, a safe plan to follow 14 ELECTRIC TRANSMISSION. 71 install 1 kilowatt of transformer capacity for every horsepowerdelivered by the motor. Thus a 20-horsepower, two-phaseinduction motor would require tA\ro 10-kilowatt transform-ers; a 30-horsepower three-phase motor would require three10-kilowatt transformers; and so on. The following table,issued by the General Electric Company, shows the size andnumber of transformers suitable for 60-cycle, three-phaseinduction motors. TABLE Till. CAPACITY OF TRANSFORMERS FOR THREE-PHASEINDUCTION MOTORS. Capacity of Transformers. H. P. Kilowatts. of Motor. Two Three Transformers. Transformers. 1 2 3 5 1 2 10 15 20 30 50 75 LINE CALCULATIONS FOR ALTERNATINGCURRENT. 84. The factors that determine the size of line wire fora direct-current transmission apply also, in a general way,to alternating-current systems. The resistance of the linecauses a drop in pressur
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