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can a DC Servo Motor generate power ?

Discussion in 'Photovoltaics' started by developer, Aug 16, 2004.

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  1. developer

    developer Guest


    a DC servo motor REV F

    P£¿N 6417317-01

    M1030-056 1180 rpm output 230 W

    Max 80A
    current 8.3A

    Sanyo DenkiCo Ltd

    can a DC Servo Motor generate power then using invertor 36V --> 220V when
    the shaft is spinning at a reasonable speed
  2. Andy Baker

    Andy Baker Guest

    Don't even bother. Yes, the servo can generate electricity, but not well at
    all. It's just a DC motor - plus it's a terrible waste of a good servo. Do
    this: Sell the servo on ebay - probably fetch $100, especially if it has an
    encoder on it, and buy a real generator, or, if you're on a budget, buy a
    used alternator out of a car. Many of them will put out well over 600 watts
    at a reasonable RPM, and with a regulator, at the voltage you need to use a
    standard inverter. To get 230W out of that servo, you'd need to spin it SO
    fast it would kill the poor thing. And I know people will say "Alternators
    are bad because they fail!!" Yes true, but slower than the servo will. Think
    of this - a typical automobile alternator lasts around 200,000 hours, in
    high temperatures, road grit, grime, solvents, excessive vibration and under
    heavy load. They're also FREE if you look hard enough.

  3. m II

    m II Guest

    I hope we're just exaggerating..200,000 hours at say, 20 mph = 4 million
    miles. You must have a very good car <g>


    __ __ __ __ __ __ __ __
    / /\ / /\ / /\ / /\ / /\ / /\ / /\ / /
    / /\ \/ /\ \/ /\ \/ /
    /_/ \/_/ \/_/ \/_/ \/_/ \/_/ \/_/ \/_/

    ..let the cat out to reply..

    ©Densa International
    'Think tanks cleaned cheap'
  4. Andy Baker

    Andy Baker Guest

    Kilometers on the brain, or gravel and small bits of wood.... heh, yeah
    right. no idea why I said that....still though, if I had to put a "good as
    used" alternator in my windmill once a year to the tune of $60, I wouldn't
    complain all that much....unless it was on a HUGE tower

  5. m II

    m II Guest

    Neither would I. although I'm surprised I haven't seen any tower units
    that send the mechanical motion to near ground level, where maintenance
    on an alternator could be done easily.

    Alternately, how about a unit+blades that slides up and down on the
    tower/pole via chain/sprockets or pulleys?

    I haven't done much research in this yet, but I'm looking for an
    alternative to 300 dollar 75 watt panels and 'single wire' GM
    alternators are relatively inexpensive.

    The search continues..

  6. Andy Baker

    Andy Baker Guest

    The crank up/down idea is good, though you couldn't have guy wires, It would
    be relatively simple to do with triangle style open tower. The trolley for
    the blade assembly would be pretty straightforard - six cupped-out
    wheels/pulleys in a hinged or bolt together configuration with 3 wheels
    above the hub and 3 below. (I say hinged or bolt together because how stupid
    would it be to have to go to the top of the tower to drop the trolley over
    the top of it) - A big steel cable would then go up through the middle and
    over the top to the trolley and voila. Hook it either to a hand crank winch
    like on a boat trailer or some other kind of braking electric winch, and
    there it is. Electrical cable would obviously have to run up the outside of
    the structure, but you could simply run a single thin piece of steel cable
    along one of the triangle flats with a series of rings fixed to the electric
    cable that also slide up and down the stationary steel cable. This would
    keep them from blowing around, and allow the electrical cable to neatly pile
    on the ground with you bring it down for maintenance. OOOOOOR...

    Some of the armature radio guys have these giant telescoping antennas that
    they can crank up and down... Obviously none of them are built to take a
    physical side to side load like a turbine would put on them, but its a good
    place to start...

    Maybe I'll do something up in solidworks..

  7. developer

    developer Guest

    alternator need to apply current to make the coil become megnatic before the
    alternator can generator power.
  8. m II

    m II Guest

    I foolishly thought residual magnetism in the rotor would start things up.

    The 'one wire' GM type of alternator has a built in regulator, so no
    external field feed is needed. You'd only need two slip rings to get
    power to the battery. Besides, with a bunch of three phase rectifier
    diodes blocking current flow backwards from the battery, I don't see how
    you could apply any juice anyways.

    Another solution is a brushless permanent magnet alternator. You'd have
    to have a regulator in the output, though.

    Harley Davidson uses a permanent magnet alternator. They are probably
    the only ones on earth. Everyone else is using three phase variable
    field setup.

    The rectifier/regulator pack for a Harley is compact and good for
    roughly 20 amps output at 13 volts. Two wire (usually) AC in, two wire
    DC out. Easy.


    __ __ __ __ __ __ __ __
    / /\ / /\ / /\ / /\ / /\ / /\ / /\ / /
    / /\ \/ /\ \/ /\ \/ /
    /_/ \/_/ \/_/ \/_/ \/_/ \/_/ \/_/ \/_/

    ..let the cat out to reply..

    ©Densa International
    'Think tanks cleaned cheap'
  9. Andy Baker

    Andy Baker Guest

    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 $5 in parts!...... it's always about
    money isn't it,...hHHhahahahaha!!

  10. brian

    brian Guest

    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
  11. 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.

  12. Andy Baker

    Andy Baker Guest

    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
  13. How efficient are they ?

    Cheers, J/.
  14. Any idea what they cost ?

    Cheers, J/.
  15. m II

    m II Guest

  16. Andy Baker

    Andy Baker Guest

    200,000 kilometers not hours :p

    Also, not very efficient, but they can put out massive amounts of power for
    their size.... if you give it to them...

    And again, dirt cheap if not free.
  17. Bob Adkins

    Bob Adkins Guest

    I think a 10-20" oilfield casing could hold a nice-sized windmill. The
    raising/lowering mechanism could be inside the casing.

    Yep, being able to work on things without climbing would make windmills much
    more attractive.
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