The motor I saw has 14 brushes spaced around a commutator that is about two feet in diameter, and is used to move a large antenna. What is the advantage of having so many brushes and is the commutator wired any differently then normal.
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3 Answers
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Multiple brushes are also needed to handle the current in the armature circuit. High power motors need multiple brushes just to handle the current and keep heating down to a reasonable level.
It isn't just motors either, here on some high power slip rings, the slip ring is 18" diameter of brass, and each one has 168 2" carbon/metal composite brushes on them. Neither carbon nor carbon/metal composites conduct anywhere nearly as well as copper.
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Having more brushes and more solenoids in stator and/or rotor of a motor makes the torque more constant. This is mostly useful if the torque needed to startup a machinery is rather high and low vibrations are desired.
If the commutator has only two contacts its wiring is not as special. But the stator will have 14 or a multiple of 14 solenoids. Those solenoids are connected in series with a brush connected to each node between two of them.
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There are two types of windings. Lap and wave. Wave winding has only two parallel paths. But lap winding has parallel paths equal to number of poles and hence it needs as many brushes. The advantage of having more parallel paths is that you can handle more current. And since torque produce is proportional to current hence more torque is produced.
