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Re: [s-w-h] RE: Induction Generator vs Induction Motor; 3 phase [asynchronous] :...:

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  • Nando
    Geoff: I would be very interested in knowing what type of passive pitch control those mills have, time after time the mills with pitch control show that they
    Message 1 of 31 , Nov 30, 2011
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      Geoff:

      I would be very interested in knowing what type of passive pitch control those mills have, time after time the mills with pitch control show that they are having longer useful life and behave better that the furling type.

      The 10 and 20 Kw ( in reality both were 20 KW ) have synchronous motors with a secondary biasing alternator to feed the rotor field and with an excellent Torque Pitch Controlled HUB that was sensitive to the wind and loading attaining a good MPPT profile though the area where they are have a wind regime of around 8.5 m/s .

      The induction motor Grid tied with a good pitch control can do an excellent job and now a days with the advances in wind monitoring and electronic controllers the induction motor windmills have the chance to produce excellent power if in a good wind regime.

      I always WONDER WHY the well known small windmill manufacturers do not bite the bullet and build a TPCH wind mill that has natural wind protection when unloaded -- the RPM drops to a set minimum even at high wind velocities if unloaded.

      Nando



      ----- Original Message -----
      From: Geoff Thomas
      To: Malcolm Hamilton
      Cc: Nando ; SWH ; Jarrett Johnson
      Sent: Wednesday, November 30, 2011 22:48
      Subject: Re: [s-w-h] RE: Induction Generator vs Induction Motor; 3 phase [asynchronous] :...:



      Hi Jarrett, a Dutch company called Lagerwey used induction motors 20 plus years ago, I will attach a brochure I made when I was their agent, they ceased trading many years ago but their 80 kW and 250kW 2 bladed variable speed teetering hub Passive Pitch machines (Hey Nando) are mostly still flying - recently I had a situation where a French company, Travere, defaulted in supply of a permanent magnet turbine, - so, money already spent, (very scary for a small business), I found an old Lagerwey 75kW, - refurbished and in good nick, to fill the hole, - oops, control and conversion gear, 100kW Inverter and container of batteries already bought, but fortunately simply by changing the software of the controller, (throwing away all the original control gear right up to the wires coming out of the generator, - it was grid connect anyway) using the motor control software, we were able to control the induction motor exactly as a generator, even to using that as an MPPT so we get the most out of the wind, - very situation specific but the principle will apply to your motor, and I am happy to say that that system has been flying beautifully since end 2009, saving the community it powers over $100,000; per year on Diesel alone.
      Using modern programmable motor control software makes induction motors more efficient and they are such basic, solid, widespread machines there are certainly good reasons to use them.
      Cheers,
      Geoff Thomas.
      Australia.

      On 01/12/2011, at 1:49 PM, Malcolm Hamilton wrote:

      > Jarrett
      >
      > The electronics associated with using a motor as a generator are
      > fairly straight forward, although the control algorithms can be
      > difficult.
      >
      > First, is a rotor speed sensor that ensures that the generator is
      > operating above synchronous speed, i.e. positive generating slip.
      > Frequently this is done by sensing the faint stator voltage waveform
      > that is created by the residual magnetism in the rotor. Alternately,
      > a mechanical or optical method could be used.
      >
      > Second, a standard motor contactor is then used to close the generator
      > to the grid (while isolating the speed sensor if it was measuring the
      > stator voltage). The contactor includes time over-current and thermal
      > trips and associated fusing and disconnects. It's beneficial to
      > include a soft start provision because the generator could be cycling
      > on and off the grid quite frequently when the wind speed is marginal.
      > That is also a good reason for over-sizing the generator because it'll
      > be seeing a fairly severe duty cycle, similar to frequent start cycles
      > for a motor. For example, I have a 30 kW turbine that uses a 50HP
      > motor.
      >
      > Third, a reverse power sensor is required to drop the generator off
      > the grid when the wind drops below synchronous speed. Otherwise you'd
      > be motoring a big fan. I've seen it happen.
      >
      > Finally, the utility will require the generator to trip out on their
      > limits for under/over-frequency, under/over-voltage and ground
      > faults. And possibly phase imbalance for a 3 phase connection. By
      > the way, they are real fussy on this stuff and may require an
      > engineer's stamp and drawings.
      >
      > Pulling all this together is best done by a micro-controller or PLC
      > for all the logical interlocks and for fine-tuning time delays. There
      > are a few vendors that sell packaged controls.
      >
      > Good luck - this is not for the faint at heart.
      > Malcolm
      >
      > PS: As Nando points, this philosophy is for an induction generator
      > (motor) that receives excitation current from the grid. There are
      > other schemes using capacitors to provide the excitation current but
      > they need to be tuned to the load.
      >
      > On 2011Nov30, at 9:16 PM, Nando wrote:
      >
      > > Jarrett Johnson:
      > >
      > > Induction Generator == induction motor -- NO one tries to spec an
      > > Induction Motor as an Induction generator.
      > >
      > > This since 1938 when it was discovered that an Induction motor when
      > > the windings are resonated and the RPM is increased above rating
      > > plus Slip the motor starts to produce power as much as a motor.
      > >
      > > The use of the induction motor as a generator requires some basic
      > > principles to make sure that it is not over loaded.
      > >
      > > Just reverse the motor curves into power
      > >
      > > Nando
      > >
      > > ----- Original Message -----
      > > From: Jarrett Johnson
      > > To: small-wind-home@yahoogroups.com
      > > Sent: Wednesday, November 30, 2011 16:51
      > > Subject: [s-w-h] RE: Induction Generator vs Induction Motor; 3 phase
      > > [asynchronous]
      > >
      > > Just looking for data right now. Has anyone heard of an induction
      > > generator manufacture? I just wanted to compare pricing vs a typical
      > > 3 phase induction motor [asynchronous]. Nord isn't really to excited
      > > to warrentee a motor that has been used as a generator. On top of
      > > that I was thinking if I could find a manufacture that supplied
      > > these for generator use they would have performance data/graphs etc.
      > > I'm thinking this would be pretty rare [if there even IS such a
      > > manufacture] but it's worth looking/asking for at least.
      > >
      > > Thanks
      > >
      > > J. Johnson
      > >
      > > [Non-text portions of this message have been removed]
      > >
      > >
      >
      > [Non-text portions of this message have been removed]
      >
      >

      [Non-text portions of this message have been removed]





      [Non-text portions of this message have been removed]
    • Malcolm Hamilton
      Thanks Nando This is an important contribution to our collective intellectual capital. It will help many small wind designers. When you combine this
      Message 31 of 31 , Dec 7, 2011
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        Thanks Nando

        This is an important contribution to our collective intellectual
        capital. It will help many small wind designers.

        When you combine this fundamental understanding of generation with
        modern power control techniques (as recommended by Claus Nyboe), then
        it opens opportunities for new designs.

        Malcolm



        On 2011Dec5, at 12:44 PM, Nando wrote:

        > THOSE INTERESTED ON THE NIGEL SMITH PAMPLET
        >
        > http://www.frenchriverland.com/
        > Motors_As_Generators_N_Smith_UK_1994.pdf
        >
        > Nando
        >
        >
        >
        >
        > ----- Original Message ----- From: "Claus Nybroe"
        > <mail@...>
        > To: "Nando" <nando37@...>
        > Cc: "Malcolm Hamilton" <hamilton47@...>; "Geoff Thomas" <wind@...
        > >; "SWH" <small-wind-home@yahoogroups.com>; "Jarrett Johnson" <hjjohnson@...
        > >
        > Sent: Monday, December 05, 2011 11:22
        > Subject: Re: [s-w-h] RE: Induction Generator vs Induction Motor; 3
        > phase [asynchronous] :...:
        >
        >
        >> Thanks Nando,
        >>
        >> Did you insert them in the coil heads sticking out of the rotor
        >> core, "N" and "S" at same side, and do do the have to belong to
        >> same coil?
        >>
        >> Realize I have to experiment :)
        >>
        >> Yes, I have also taken the Nigel Smith book out of the shelf over
        >> the years.
        >>
        >> "Motors as generators for micro-hydro power"
        >> Nigel Smith
        >> Intermediate Technology Publications
        >> Intermediate Technology Development Group 1994, reprinted 1997
        >> ISBN 185339 286 3
        >>
        >> Claus
        >>
        >>
        >>
        >>
        >>
        >>
        >> Den 05-12-2011 17:34, Nando skrev:
        >>> Claus:
        >>>
        >>> I used two sets of two magnets opposed at each end -- and 180
        >>> degrees.
        >>>
        >>> You need to insert then rotate the motor to read the generated
        >>> voltage
        >>> which it produced around 8 to 12 volts that with the windings
        >>> resonated
        >>> with capacitors produced the high voltage.
        >>>
        >>> Those trying to use induction motors as generators should study
        >>> Nigel
        >>> Smith pamphlet and then download all those articles available that
        >>> have
        >>> studied the motors as generators to learn and to understand how the
        >>> voltage is generated and the voltage level increment due to the
        >>> RPM of
        >>> the motor and as well the generated frequency.
        >>>
        >>> Too often I read here the efforts of many with the induction
        >>> motors --
        >>> that show and indicate that the "experimenter" has not done the
        >>> proper
        >>> steps in the learning process to attain the proper and practical
        >>> results
        >>> and at the same time to learn the behavior of the motor when
        >>> driven by a
        >>> power mechanical source and how the voltage output varies
        >>> depending on
        >>> the RPM of the motor and as well the frequency generated
        >>>
        >>> AS a example a 1500 RPM RESONATED induction motor rated 240 Volts
        >>> 50 HZ
        >>> if rotated around 2400 RPM the generated Voltage can go as high as
        >>> 500
        >>> to 600 Volts AC.
        >>>
        >>> Nando.
        >>>
        >>>
        >>>
        >>>
        >>> ----- Original Message ----- From: "Claus Nybroe" <mail@...
        >>> >
        >>> To: "Nando" <nando37@...>
        >>> Cc: "Malcolm Hamilton" <hamilton47@...>; "Geoff Thomas"
        >>> <wind@...>; "SWH" <small-wind-home@yahoogroups.com>; "Jarrett
        >>> Johnson" <hjjohnson@...>
        >>> Sent: Monday, December 05, 2011 10:09
        >>> Subject: Re: [s-w-h] RE: Induction Generator vs Induction Motor; 3
        >>> phase
        >>> [asynchronous] :...:
        >>>
        >>>
        >>>> >then experimenting I used Small Alnico magnets inserted in the
        >>>> windings - which solved the problem for good -- allowing turn ON or
        >>>> OFF -- <
        >>>>
        >>>> I've tried this one time Nando, but it did not work for me. Do you
        >>>> remember how you inserted your Alnico magnets?
        >>>>
        >>>> Claus
        >>>>
        >>>>
        >>>>
        >>>>
        >>>>
        >>>
        >
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