The Alternator
المؤلف:
GEORGE A. HOADLEY
المصدر:
ESSENTIALS OF PHYSICS
الجزء والصفحة:
p-410
2025-12-14
49
If the coils of a dynamo are coupled to copper rings instead of to the bars of a commutator, the current will be an alternating one, changing its direction twice for every rotation of each coil (Fig. 1). By using as many pole pieces to the field as there are coils, and by coupling the coils properly, the currents in all the coils are put in series, giving an alternating current of high E. M. F. The field magnets of an alternator are usually magnetized by a current from a small direct-current machine called an exciter. Figure 2
shows the exciter at the right, belted to the pulley on the alternator shaft: its current is fed into the stationary field magnets supported by the frame. The armature coils are wound as flat coils on the surface of the rotating core.
Figure 3 represents an alternator with revolving field magnets and a stationary armature. In this machine the exciter is direct connected, that is, run on the alternator shaft. The collector rings, outside the commutator of the exciter, lead its current to the field of magnets. The armature wire is wound in slots on the inside of the stationary frame, and the cutting of the lines of force is produced by the sweeping of the rotating magnetic field across the stationary conductors.
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