Identifier: cyclopediaofappl05amer (find matches)
Title: Cyclopedia of applied electricity : a general reference work on direct-current generators and motors, storage batteries, electrochemistry, welding, electric wiring, meters, electric lighting, electric railways, power stations, switchboards, power transmission, alternating-current machinery, telegraphy, etc.
Year: 1916 (1910s)
Authors: American Technical Society
Subjects: Electric engineering
Publisher: Chicago : American Technical Society
Contributing Library: Northeastern University, Snell Library
Digitizing Sponsor: Northeastern University, Snell Library

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te them on systemsusing GOO volts, they can be run at the same speed as on 1,200-voltlines by simply connecting all four motors in parallel. In high-voltage equipments the lamps, control circuits, andin some cases the air compressors, are supplied with GOO-volt current.This permits the use of standard apparatus. These circuits areconnected between trolley and ground through a machine knownas a dynamotor, which, as its name implies, is both a generator anda motor. It is a small direct-current, compound-wound motorwith two windings on the armature, and two commutators, one oneach end of the shaft. The two armature windings which are shown diagrammaticallyas A and A in Fig. 79 are connected in series across the line.Current at one-half line voltage is taken off between the left-hand terminal and the center (the point marked In) of the seriesfield /, and then sent through the control circuits, etc. If theequipment were designed to operate on high-line voltage con- 172 ELECTRIC RAILWAYS 77
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173 78 ELECTRIC RAILWAYS tiimously, no additional equipment in the control circuit wouldbe required. This apparatus, however, is designed to operate oneither 1,200- or 600-volt circuits, and as the dynamotor is not neces-sary at the lower voltage, some device must be used to cut it outof the circuit when it is not needed and to connect the controlcircuits direct to the trolley. This adjustment is accomplished bythe aid of a special form of relay and a switch. The relay is shown diagrammatically in Fig. 79. It consistsof a coil and core with a pivoted iron armature M above. Whenthe coil is energized the core attracts the armature. The armaturecarries a switch arm which makes and breaks contact at 15. Belowthe coil is a second pivoted switch arm N, which makes and breakscontact at 13 and 14- The lower arm is connected with the upperby the link represented by the dash line. The positions of the mov-ing parts of the relay, as shown in the diagram, are for 1,200-voltoperation the solenoid

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