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can a DC Servo Motor generate power ? - Page 3

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Posted by m II on August 19, 2004, 7:17 am
John Beardmore wrote:

This place has it for 170$ US. Rotor, Stator and regulator.


I keep forgetting the motors rev to a bit over six thousand rpm, so to
get any output on a windmill, some serious gearing up would have to be
done...same as a car alternator.


Posted by Andy Baker on August 17, 2004, 1:36 pm
So? When you have a turbine and PV's what are you doing most of the time?
charging batteries... still though, you might need to come up with something
that would turn the field coils off if the current went too high (as in when
the wind stopped) and come back and check every few minutes to see if it's
started again... This would keep your "kicker" battery from getting drained
too fast for prolonged periods of calm conditions.

logic goes like such:

1. Activate field coils.
2. A few seconds later, Check field coil current and output voltage.
3. If field current coil is less than 2 amps and voltage at least 13 V
    then go back and repeat step 1. If not, continue to step 3.
4. Disconnect field current
5. Wait 5 minutes
6. Go to step 1.

This process could easily be controlled by a simple PIC - for the extra
handy folks, you could even program the PIC to provide the alternator field
coils with the appropriate PWM signal, then you wouldn't even need the
expensive regulator..... The old alternator I was playing with I got in
exchange for an ice cold six pack of beer on a hot day down at the local
garage. Maybe I should start selling pre-programmed 8 pin PICS on a board
with a MOSFET and a couple diodes and a comparator...a voltage divider... a
zener..hold on!! we're almost up to $ in parts!...... it's always about
money isn't it,...hHHhahahahaha!!



Posted by brian on August 18, 2004, 10:48 am


Old farm pumping mills used to have a shaft drive down to the base, but I
have never seen a generator built in the same way but cannot see any reason
why not except may be losses and complications  through the 90 deg. box.
other wise it would be a hydraulic drive, but this could prove very

Posted by Anthony Matonak on August 18, 2004, 3:16 pm
 brian wrote:

Pumping windmills still often use a mechanical drive in one form
or another. One version uses an air compressor at the turbine and
an air hose leading to the pump itself.

I believe the reason why they don't do this with electric wind
turbines is that a well designed generator doesn't need much,
if any, maintenance. There isn't any particular reason to place
the generator at ground level and lots of good reasons to place
it up on the tower with the turbine. For one, these designs
are less complex, weigh less and are more efficient.


Posted by Andy Baker on August 18, 2004, 3:44 pm
 The reason they did a gear box is because inevitably, the pump required
mechanical energy at the base of the unit - it just made more sense. The
output was going to have to run through a gearbox somewhere, so it didn't
matter. Electricity on the other hand, doesn't loose horsepower if you run
the wires around a corner. The general rule of thumb I guess is as follows -
"2% of the rated input HP per loaded gear mesh"

So there you go. If you can spare 2% of your windmill power, screw around
with shaft alignment, deal with the fact that it's going to flex the tower
when the wind blows, etc... then I say go for it!

Andy Baker


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