[Electric engineering.] . DESCENT LIGHTING. 91. The type of dynamo used for operating a lightingsystem will depend on the method of distribution construction of the dynamo will also depend to someextent on the method used for driving it; , on whetherit is driven by means of a belt or coupled directly to thesteam engine or waterwheel. We will consider, briefly, afew of the different types used in order to point out some oftheir distinguishing features. DIRECT-CURRENT DY1STAMOS. 92. Belt-Driven Dynamos.—Dynamos used for oper-ating incandescent lamps on the two-wire or three-wires
[Electric engineering.] . DESCENT LIGHTING. 91. The type of dynamo used for operating a lightingsystem will depend on the method of distribution construction of the dynamo will also depend to someextent on the method used for driving it; , on whetherit is driven by means of a belt or coupled directly to thesteam engine or waterwheel. We will consider, briefly, afew of the different types used in order to point out some oftheir distinguishing features. DIRECT-CURRENT DY1STAMOS. 92. Belt-Driven Dynamos.—Dynamos used for oper-ating incandescent lamps on the two-wire or three-wiresystems are almost invariably compound-wound. Shunt-wound machines were used some years ago for this purpose,but the compound-wound machine is much better, since itkeeps the voltage at the right value automatically. Usuallythe machines are overcompounded, so as to give a rise in 82 ELECTRIC LIGHTING. 16 voltage from no load to full load corresponding to the dropin the line, and thus keeping the pressure at the lamps con-. stant. Modern dynamos used for this purpose are nearlyalways of the multipolar type. Two-pole machines were § 16 ELECTRIC LIGHTING. 83 formerly much used, but these have given place to the mul-tipolar type. All the dynamos used for any kind of workmay be divided into two classes, according to the methodused for driving them, i. e., belt driven and direct con-nected. Fig. 49 shows a Wood eight-pole compound-wound dynamoas used for lighting on a 110-volt, two-wire system, or110-2*20-volt, three-wire system. This machine is mountedon rails R, so that the tension of the belt may be adjustedby sliding the machine by means of the ratchets T, T. Themagnet yoke A is circular and is provided with eightinwardly projecting poles, each of which is provided with afield spool B. Each of these spools is provided with twowindings: a shunt winding, consisting of comparatively finewire, and a series winding, usually of copper strip or heavywire, capable of carrying the whole
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