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Re: (ET) E20 lacking power



At 10:19 AM 2/23/05 -0500, Markus Lorch wrote:
Anyhow, after fixing all these things the AA still doesn't run nearly
as good as my E20 CC tractor. It simply draws way to much current for
what it does. This was the case with the vibrating E20 motor and didn't
get better with the good E15 motor. D2 speed is basically useless as
the power meter rarely leaves the red zone unless I am going downhill
and D1 ends up being faster or as fast for all intents and purposes.

On my other E20 the D2 speed is still beefy and only goes into the
red if I drive up hill with full field weakening etc.

Yesterday I did a 30 min full-power test (power needle always in
the red, 50% at the far right end of the meter) run in Speed 4-8, to see
what if something heats up. Here the results:
- all battery posts and cables remain cold
- motor armature posts get warm, motor outside remainded cold
- klixon connections on motor got pretty warm, almost too warm to
  for more than a second but klixon didn't fire (yet)
  (I'd guess it was not long enough)
- all contactor posts on the F and R contactors got warm, one got
  to the point where it was almost too hot to touch
- power resistors stayed cold
- FW shunt was sizzling (and smelling :) - didn't try touching it

The performance of the tractor under this condition was mediocre, the
battery voltage on any pair of the batteries almost never dropped
below 11.5V only once did I get it down to 10.5V which was when I almost
stalled the tractor in D2 on a steep incline, speed 4. (I could never do
that
with my other E20). I estimate that I was pulling more than 500A at
this point (based on the power meter being all the way to the right)
which would be over 15kw of power.

This may be off base (I'm not familiar with the motors involved) but these are similar to what I would expect for a wrongly sized field weakening resistor (resistance too low). Although in that case the armature is likely to heat as well. Did you move the field weaken resistor with the motor or keep the one in the tractor that was there originally?

Robert


" 'Freedom' has no meaning of itself.  There are always restrictions,
be they legal, genetic, or physical.  If you don't believe me, try to
chew a radio signal. "

                        Kelvin Throop, III