In large multipolar dynamos it is, as a rule, inadvisable to have more than 100 or 150 amperes in any one circuit, except in the case of special machines for electro-chemical work. Such considerations are factors which govern the choice of number of circuits.
Equalizer Rings.—These are rings resembling a series of hoops provided in a parallel wound armature to eliminate the effects of "unbalancing," by which the current divides unequally among the several paths through the armature. By means of leads, equalizer rings connect points of equal potential in the winding and so preserve an equalization of current.
Fig. 278.—Rear view of armature of a large dynamo built by the General Electric Co., showing equalizer rings.
Ques. In multipolar machines what points are connected by equalizer rings?
Ans. Any two or more points in the winding, that during the rotation, are at nearly equal potentials.
If there were perfect symmetry in the field system, no currents would flow along such connectors; however, owing to imperfect symmetry, the induction in the various sections of the winding may be unequal and the currents not equally distributed.
Drum Winding Requirements.—There are several conditions that must be satisfied by a closed coil drum winding:
1. There cannot be an odd number of inductors;
An odd number of inductors would be equivalent to not having a whole number of coils. The even numbered inductors may be regarded as the returns for the odd numbered inductors.