Fig. 279.—Current distribution in a gramme ring armature. There are two paths for the current between the brushes, half going up each side of the ring as indicated by the arrows, thus giving two paths in parallel as indicated in [fig. 281].
Fig. 280.—Battery analogy illustrating current distribution in a ring armature. The eight coils of the armature, [fig. 279], are represented by two batteries of four cells each. The action of the two units thus connected is indicated by the arrows. In the external circuit the voltage is equal to that of one battery and the current is equal to the sum of the currents in each battery.
The two batteries being connected in parallel, the voltage at the terminals will be the same, but the current will be the sum of the currents in each battery.
Ques. How may the number of paths in parallel be increased?
Ans. By increasing the number of poles.
For instance, in a four pole machine, as in [fig. 283], there are four paths in parallel. In this case the armature may be used to furnish two separate currents, though this is not desirable.
Fig. 281.—Diagram showing distribution of current in the gramme ring armature of [fig. 279]. The current flows in two parallel paths as indicated.