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The Commutator

المؤلف:  GEORGE A. HOADLEY

المصدر:  ESSENTIALS OF PHYSICS

الجزء والصفحة:  p-405

2025-12-13

408

In order that the current taken from the coils of a dynamo may be in one direction, the ends of the coils are connected with copper terminals that revolve with the shaft, and the currents are taken off by fixed brushes. A two-part commutator, suitable for a single coil, is shown in Fig. 1. A study of this figure will show that the brushes can be placed in such positions that the change from one commutator bar to the other shall take place just as the direction of the current in the coil changes; and for this reason, the current in the external circuit will always be in one direction.

The commutator usually consists of as many copper bars, or segments, as there are coils of commutator wire. Figure 2 shows the commutator ready to be fixed to the dynamo shaft. Each bar has a radial projection at one end with a slit in it, into which two wires are soldered. These wires are the end of one coil and the beginning of the next. The commutator bars are insulated from each other by mica strips and from the shaft by thin mica rings.