Ques. What is the effect of a multiplex winding?
Ans. It reduces the tendency to sparking, because only half of the current is commutated at a time, and also because adjacent commutator bars belong to different windings.
Fig. 272.—A progressive wave winding. If the front and back pitches of a wave winding be such that in tracing the course of the winding through as many coils as there are pairs of poles, a segment is reached in advance of the one from which the start was made, the winding is said to be progressive. The figure shows three coils of a winding having 18 inductors. From the definition, the number of coils to consider to determine if the winding be progressive is equal to the number of poles divided by 2, which in this case is equal to 2. These coils are shown in the figure as follows: A—1—4—F and F—11—14—B. The second coil ends at segment B which is in advance of segment A from which the winding began, indicating that the winding is progressive. Fig. 272 is given simply to illustrate the definition of a progressive winding, and not to represent a practical winding.
Ques. Does an accident to one winding disable the machine?
Ans. No, it simply reduces its current capacity.
Ques. Can multiplex windings have more than two windings?
Ans. Yes, there may be three or four windings.
Ques. What is the objection to increasing the number of windings?
Ans. It involves an increased number of inductors and commutator segments, which is undesirable in small machines, but for large ones might be allowable.