. The practical telephone handbook and guide to the telephonic exchange . Fig. 307 wire between each connection. The greater the number ofcoils into which the armature is divided and the greater thenumber of commutator plates, the steadier will be thecurrent derived from it if the driving speed is kept the generator most generally used for telephone work thenumber of armature windings and commutator plates is 175. Dynamos are called series or shunt machines ac-cording to whether the field-magnet coils are joined up inseries or in shunt with the armature. Shunt machines are THE POWE
. The practical telephone handbook and guide to the telephonic exchange . Fig. 307 wire between each connection. The greater the number ofcoils into which the armature is divided and the greater thenumber of commutator plates, the steadier will be thecurrent derived from it if the driving speed is kept the generator most generally used for telephone work thenumber of armature windings and commutator plates is 175. Dynamos are called series or shunt machines ac-cording to whether the field-magnet coils are joined up inseries or in shunt with the armature. Shunt machines are THE POWER PLANT 305 generally used in telephony, as giving a steadier current, andone in which the voltage can be more readily adjusted. The f n -i N © l—LX^ s EXT. CIRCUITFig. 308. EXT CIRCUITFig. 309 magnet coils of shunt machines are generally wound to a muchhigher resistance than the armature. In compounddynamos a combination of both seriesand shunt windings is used. Figs. 308, 309 and 310 show howthe field-magnet coils are connectedin a series, a shunt, and a compounddirect current dynamo respectively. Motors. — Dynamo machines aregenerally reversible, so that if cur-rent is sent through the machinefrom some outside source, and thebrushes are in the proper position,the armature will be subjected to a torque —that is, a force tendingto drive it round. The machine then becomes a motor, and can be used for driving othermachines. Thus motors are of similar construction todynamos. Motor Generators.—Fot obtaining the battery-chargingcurrent the method most frequently adopted when an out-
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Keywords: ., bookcentury1900, bookdecade1900, booksubjecttelephone, bookyear19
