RE: (ET) E20 lacking power

["Markus Lorch" <mlorch vt edu>]

> 
> 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?
> 

Thats a good point Robert, thank you. I did keep the original E20 
controls incl. all the field weakening resistors. However, the lack
of power is also present in speed 4 where I use no field weakening.

I should probably constrain my comparisons to speed 4. In this case
I did manage to almost stall the tractor on an incline in D2, this
never happens with my good E20 on the same incline. It will slow
down but the power meter will barely go into red when I go up there
in speed 4, D2. 

The E15 motor looks really good inside and runs smoothly. I think it has
never seen hard work as the commutator is very smooth and the brushes 
are still at 50%. I was thinking that it should be able to put
out almost as much as the E20 motor in peak power. Looking at the
motor charts, with full field the E20 motor should produce about 
29 lb-ft at 300A/1400RPM ... the E15 motor should procude about
25 lb-ft at 300A/900RPM.... hmm, the RPM are significantly different
here .....

Markus