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Re: (ET) Faster speeds in reverse
The compensation winding in our ET traction motors, which is in series
with the armature, weakens the field when the motor is running forward.
Without a compensation winding DC motors, running in the forward
direction, will slow the heavier the load (current draw) is. If the
compensation is set to weaken the field under load the effect is to
speed the motor up. GE just had to size the compensation winding to
weaken the field just enough that the motor only slowed down a little
under load, not speed up.
No, in forward the field gets *stronger* as load increases. This slows
down the motor, reduces current draw, and is a nice thing. In reverse
though the armature changes direction but the field does not. Thus it
speeds up the motor as armature current increases.
GE by using the compensation this way reduced tractor speed changes due
to hills and the like. I know my E15 doesn't slow all that much going up
hill, at least in the lower motor speeds of 1, 2, and 3.
E15 might be different. You can test this by putting the tractor in
neutral, then listening to the RPM in full field forward and full field
reverse. Reverse will sound faster.