[Electric engineering.] . e a largenumber of lamps are operated, it is usually necessary tohave several distinct feeders running to the different districtsto be lighted or supplied with power. Some of these feedersmay be long, others quite short. In order, therefore, tokeep the cross-section of the long feeders within a reasonablesize, a larger drop must be allowed in them than in the 48 ELECTRIC LIGHTING. 16 short feeders. It is necessary, then, to have some means ofsupplying the long-distance feeders with a higher pressurethan those supplying the nearby districts. Of course, thevoltage on th
[Electric engineering.] . e a largenumber of lamps are operated, it is usually necessary tohave several distinct feeders running to the different districtsto be lighted or supplied with power. Some of these feedersmay be long, others quite short. In order, therefore, tokeep the cross-section of the long feeders within a reasonablesize, a larger drop must be allowed in them than in the 48 ELECTRIC LIGHTING. 16 short feeders. It is necessary, then, to have some means ofsupplying the long-distance feeders with a higher pressurethan those supplying the nearby districts. Of course, thevoltage on the short feeders might be cut down by insertingresistance in series with them, and this, in fact, has beendone in some cases. Such a method is, however, wastefulof power and is not to be recommended. 59. A common method is to use separate dynamos forsupplying the long-distance feeders, and simply run thesedynamos at a higher voltage than those supplying the shortfeeders. This is an excellent method where the separate /est/. Fig. 30. dynamos are available, but frequently this is not the only one dynamo or set of dynamos is at hand foroperating the whole system, the best plan is to run themachines at the lower pressure suitable for the short feeders,and use a ?booster to raise the voltage on the other § 16 ELECTRIC LIGHTING. 49 feeders. Fig. 30 will indicate what is meant by this arrange-ment. The plan shown is for the three-wire system, thoughthe same scheme may be used on a two-wire system and is, infact, largely used on such systems in connection with electricrailways. In Fig. 30, A and B are two dynamos operatingon the three-wire system and supplying current directly tothe short feeders 1, 2, 3, 1, 2, 3. Feeders a, b, <rand«, b, crun to outlying points and, therefore, must be supplied witha higher pressure than the other feeders. We will suppose,for example, that each dynamo generates 125 volts and thatthe long-distance feeders require 140 volts between the out-
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