Nice writeup, Chuck.
One question comes to mind first. How much resistance across the commutator / brush assembly?
I ask because the loss through that setup might be considerable if the resistance is much at all.
Those I^2 R losses are hard to beat.
Just with round numbers if its .1 ohm per brush pair you will see 90 watts lost in each pair of brushes at 30 amps output. [.1*[30*30]] or .1 * 900.
Just curious.
Cheers.
TomW
"Education consists mainly of what we have unlearned."--Mark Twain