Question regarding DC motor commutator construction

[GoHeels247]

I'm a little confused about the commutator segments and how they are constructed. Are so many of the "bars" grouped together for each magnetic pole? For instance, we have a motor here that has at least 100 segments, does each segment alternate n-s-n-s pole? Or are several bars together? It would look like they would have to be together. If there are only 4 poles in a given motor, the armature can only change polarity every 45(360/8) mechanical degrees, right?

 

[waross]

The number of bars is related to the number of slots. The poles don't change polarity, areas on the rotor between the slots change polarity.

Bill
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"Why not the best?"
Jimmy Carter

 

[eeprom]

There are four poles in the stator of the motor, but there are many poles on the armature. I believe that there are 50 if you have 100 slots. So your rotor has 50 coils arranged in the rotor slots, they are 7.2 degrees apart. The commutator brushes are large enough that several of the poles in the rotor may be energized at one time.

 

[waross]

Not quite the way it works. The armature windings are in series and taps go the the commutator segments. A pole is formed by all the coils between each brush set. The brushes are typically the same width as the segments. One coil is shorted by each brush as the brush crosses from one segment to the other.

Bill
--------------------
"Why not the best?"
Jimmy Carter