"Due to armature reaction, the natural direction of the magnetic field of the poles is distorted. Thus the neutral plane is also altered. Therefore, the armature conductors are not at zero potential when they come in contact with the brushes. This leads to sparking across the brushes and loss of power."
I've seen that statement in various different videos regarding the subject. However I'm confused. I understand how the neutral plane shifts due to armature reaction, but I'm wondering why the armature needs to be at zero potential when it comes in contact with the brushes?
Aren't brushes supposed to transfer the current generated in the armature to the load? Why would the armature have zero potential, when in contact with the brush?
Any help would be appreciated, thanks!