Is there a single open in the armature winding?

[John1397]

TL;DR

Are all armatures with brushes wound the same

I am testing an ac armature ohms all seem ok except for to spots 180 degrees apart on opposite side the ohms are higher than the rest when measuring from bar to bar. I do not know from the readings if I have two opens or just one. To me it seems I have no shorts just opens. I made diagram of readings.

 

[Baluncore]

If the brushes are still in contact with the commutator then the readings may be asymmetric because brush connected external circuits can lower the resistance.
The different brushes may rest on one, two or three bars of the commutator.
An armature can be wound as a Lap or a Wave.

The Coil and Winding Testing Notebook can be found here.
Resistance Testing is on page 18.

 

[2milehi]

I am more familiar with dc motors. It appears that the armature is lap wound. I could imagine that you have a single open and you would be measuring the rest of the laps and arrive at the 31 Ω value. But you have two sections that are 180° apart and both measure 31 Ω. This appears to be intentional.

Are there two rows of brushes?