. Elements of electric traction for motormen and others . s are insulated from one another, andthe whole is fnounted on, and insulated from, a suitable spindle, so 48 ELEMENTS OF ELECTRIC TRACTION that the coil can be rotated. Bearing on the rings are two contactfingers, or brushes, which conduct the current to the external the coil is in the position shown, current will be passing outof the ring marked A, going through some external circuit, say, andreturning back through the ring marked B, a complete circuit thusbeing provided not only from and to the dynamo, but also throughthe
. Elements of electric traction for motormen and others . s are insulated from one another, andthe whole is fnounted on, and insulated from, a suitable spindle, so 48 ELEMENTS OF ELECTRIC TRACTION that the coil can be rotated. Bearing on the rings are two contactfingers, or brushes, which conduct the current to the external the coil is in the position shown, current will be passing outof the ring marked A, going through some external circuit, say, andreturning back through the ring marked B, a complete circuit thusbeing provided not only from and to the dynamo, but also throughthe dynamo. By the time the coil has gone halfway round, orthrough 180°, it will be found that the conductor connected to ringA is cutting across the magnetic lines in the reverse direction;also in a similar manner the one connected to B; consequently, thepressure will be reversed, and hence the direction of current will alsobe reversed. In this way, current will flow first one way throughthe circuit, and then the opposite way. Such a current is called an. Fia. 15. alternating current, and the arrangement shown in Fig. 14 is reallythe simplest possible form of an alternating generator. For most traction purposes continuous current is employed, andconsequently a generator built on these lines would not be suitablefor supplying current direct to the trolley wire. Referring now to Fig. 15, a different arrangement will be seen:one end of one conductor is connected to a half-metal ring, and theother conductor connected to another half-metal ring, the half-ringsbeing insulated from one another. It will be seen from the figurethat current is passing, when the coil is in the position sho^vn,from the half-ring A to the top brush, and from there through theexternal circuit back to the bottom brush, and so to the other half-ring B. On moving the conductors round halfway, namely, PRINCIPLE OF THE DYNAMO 49 through 180° just as before, it will be noticed that the conductorconnected to A will
Size: 2000px × 1249px
Photo credit: © Reading Room 2020 / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1900, bookdecade1900, bookpublishernewyorkvannostrand
