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RE: (ET) E20 lacking power
Hmm, you know what.. I guess the field of the smaller
motor has a different resistance. I will measure
tonight. The control card components (3 20 Ohm resistors
and 1 10 Ohm resistor) are tailored for the 18 Ohm
field of the E20 motor.
If I calculate the voltages I should see on the field
for the 18 Ohm field of the E20 then this should be
something like
0 Ohm FW 34.5V
20 Ohm FW 32.0V
40 Ohm FW 16.2V
60 Ohm FW 10.8V
70 Ohm FW 9.3V
(not certain that my calculations are correct)
I suspect that the E15 motor field is somewhere around
12 Ohms ... thus stronger field ... which would also
explain why it is a slower running motor and has a
larger pulley (4.5" than the 3 7/8 pulley of the E20
motor). 12 Ohms would about explain the voltages
I see.
I'll measure tonight.
Markus
> -----Original Message-----
> From: Christopher Zach [mailto:czach computer org]
> Sent: Thursday, February 24, 2005 9:33 AM
> To: Markus Lorch
> Cc: 'SteveS'; 'et'
> Subject: Re: (ET) E20 lacking power
>
>
> You have something seriously screwed in your field current.
> Field should
> be about battery power; it should never drop that low on
> speeds 7 and 8;
> that's basically using the compensation windings as a field.
>
> Chris
>
> Markus Lorch wrote:
> > Thanks for all your replies.
> >
> > Based on Steve's suggestions I did some measurements
> > this evening. The following table shows the voltages
> > I measured in the different speeds with the transmission
> > in neutral. I later measured under load and the only
> > major difference was the armature voltage that caved
> > in on heavy loads mainly in speeds 1-3, which was
> > expected.
> >
> > Speed Armature Field Battery
> > 1 29.8 34.5 37.5
> > 2 30.6 34.4 37.3
> > 3 31.6 34.4 37.3
> > 4 33.6 33.4 37.0
> > 5 35.5 33.2 37.0
> > 6 35.5 11.7 36.7
> > 7 34.7 8.1 36.7
> > 8 34.4 5.5 36.5
> >
> > I was puzzling why the field current is lower
> > than the battery. The voltage drop from the
> > diodes shouldn't be that much (0.7V, right?).
> > So maybe I should revisit that circuit to make
> > sure I provide a high enough voltage to the field.
> >
> > The performance of the tractor while driving it around
> > seemed a bit better than yesterday. Maybe the field
> > connector wasn't seated right and had a high resistance.
> > Running in D2 is now mostly in the yellow area
> > except when going up inclines.
> >
> > Markus
> >
> >
> >>>Also poor motor performance and large currents is usually
> >>
> >>associated
> >>
> >>>with a weak (or missing) field. You may want to hook up the
> >>
> >>voltmeter
> >>
> >>>across the field terminals and check that it's 36V when in
> >>>cruise mode -
> >>>actually I guess anything below the field weakening setting
> >>>should be 36V?.
> >>>
> >>
> >>These are good points. Too low a field could really be the
> problem and
> >>I haven't measured the field voltage after I fixed the
> >>diodes, so I think
> >>this is a good thing to check.
> >>
> >>Thanks
> >>
> >>Markus
> >>
> >>
> >>>SteveS
> >>>E20
> >>>
> >>>
> >>>
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> >>
> >>
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> >
> >
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