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INDUCTION MOTORS GRID & GRIDLESS

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  • garciah
    It is interesting the commentaries of many that set their thought to just one way and by no means they change it, though they have in front of them the
    Message 1 of 3 , Jan 31, 2003
      It is interesting the commentaries of many that set their thought to just
      one way and by no means they change it, though they have in front of them
      the pointers to make different decisions or analysis of a problem,

      It is known that you can convert and induction motor into a generator by
      adding bias capacitance or by applying the GRID AC to one of the windings.

      For those that are using relays, now days, that is a problem that indicates
      that they need technical advice or technical know-how to properly assemble a
      relay-less system using either SCR or Triacs.
      Also the technology is available to do a capacitance bank that can be varied
      in value at will, it has been done for many years.

      The induction motor/generator biased using the grid connection for the
      generation of power, indicates that this is an old problem that was solved
      many years ago.

      Now, can any one think a way that can be used to do the same thing without
      the need of having the grid power and still be able to generate power using
      induction motors without capacitors ?.

      I give you this thought, lets see if anyone can give an idea and solution to
      this problem that has been in front of you for a long time.

      A challenge is presented to all of you, or like they say in Texas :You'll

      Regards

      Nando






      ----- Original Message -----
      From: <o.krug-ei@...>
      To: <awea-wind-home@yahoogroups.com>
      Sent: Thursday, January 30, 2003 2:46 PM
      Subject: [a-w-h] Re: Twist can stay constant :-)


      > We have tried induction generators on wind turbines here for a while.
      > Our smallest turbine was the GEV 4/2 (4m diameter, 2kW) and it has
      > been used for battery charging. The problem with induction generators
      > is when the load changes. That's why it's not a problem for grid tie
      > systems but as soon as you have a varying load (e.g. battery charging
      > or pumping) you would need some kind of varying capacitors to keep
      > the generator excited according to the load otherwise you have to
      > decide that the turbine will only get loaded at a certain voltage.
      > But this does not solve the thing : the turbine just halts suddendly,
      > then starts again, and halts and starts and so on and the contactors
      > you may have between the generators and the load don't last long.
      >
      > According to me, induction generators should be kept for grid tie
      > systems. They then get excited by the utility and no capacitors are
      > needed.
      >
      > Concerning the way to have some kind of power/speed perfect cubic
      > curve... what could be done would be to draw the turbine's efficiency
      > curve vs windspeed. I mean chosing a nominal RPM per windspeed that
      > would allow to get the best power without slowing the turbine down
      > nor putting it in a dangerous state (spinning too fast). Out of this
      > curve, select 10 to 20 points and then have one of these small genius
      > things such as the Logo of Siemens to divert the output to the
      > battery load and the dump load in order to always have the best load
      > vs windspeed. The Logo gets the RPM out of the generator's 3Ph
      > voltage (as its a PMG, it's linear) and checks the voltage of the
      > battery bank. Combining the two results through a simple program
      > using the Logo's internal possibilities, you can decide whether
      > you'll send 10% to the dump load at point 1, 12% at point 2 and so
      > on... or whether you wish to limit the amps (and therefore the load)
      > at low wind speeds.
      >
      > These are just ideas but it would actually be a real MPPT fo a wind
      > turbine, keeping it loaded all time long but exactly as you wish it
      > to be loaded.
      >
      > Olivier.
      >
      >
    • jim barr
      Jim Barr http://homepage.ntlworld.com/wandana expert to Manic Mechanics Wind powered coffee grinders (2000) Best is the enemy of good enough Barrs Law of
      Message 2 of 3 , Feb 1, 2003
        Jim Barr
        http://homepage.ntlworld.com/wandana
        expert to Manic Mechanics Wind powered coffee grinders (2000)

        Best is the enemy of good enough


        Barrs Law of Recursive futility
        If you're smart enough to use one of these....
        .....you can probably manage without one!


        -----Original Message-----
        From: garciah [mailto:garciah@...]
        Sent: 01 February 2003 05:03
        To: awea-wind-home@yahoogroups.com; o.krug-ei@...
        Subject: [a-w-h] INDUCTION MOTORS GRID & GRIDLESS


        It is interesting the commentaries of many that set their thought to just
        one way and by no means they change it, though they have in front of them
        the pointers to make different decisions or analysis of a problem,

        It is known that you can convert and induction motor into a generator by
        adding bias capacitance or by applying the GRID AC to one of the windings.

        For those that are using relays, now days, that is a problem that indicates
        that they need technical advice or technical know-how to properly assemble a
        relay-less system using either SCR or Triacs.
        Also the technology is available to do a capacitance bank that can be varied
        in value at will, it has been done for many years.

        The induction motor/generator biased using the grid connection for the
        generation of power, indicates that this is an old problem that was solved
        many years ago.

        Now, can any one think a way that can be used to do the same thing without
        the need of having the grid power and still be able to generate power using
        induction motors without capacitors ?.

        YES


        <snip>

        Regards

        Nando






        ----- Original Message -----
        From: <o.krug-ei@...>
        To: <awea-wind-home@yahoogroups.com>
        Sent: Thursday, January 30, 2003 2:46 PM
        Subject: [a-w-h] Re: Twist can stay constant :-)


        > We have tried induction generators on wind turbines here for a while.
        > Our smallest turbine was the GEV 4/2 (4m diameter, 2kW) and it has
        > been used for battery charging. The problem with induction generators
        > is when the load changes. That's why it's not a problem for grid tie
        > systems but as soon as you have a varying load (e.g. battery charging
        > or pumping) you would need some kind of varying capacitors to keep
        > the generator excited according to the load otherwise you have to
        > decide that the turbine will only get loaded at a certain voltage.
        > But this does not solve the thing : the turbine just halts suddendly,
        > then starts again, and halts and starts and so on and the contactors
        > you may have between the generators and the load don't last long.
        >
        > According to me, induction generators should be kept for grid tie
        > systems. They then get excited by the utility and no capacitors are
        > needed.
        >
        > Concerning the way to have some kind of power/speed perfect cubic
        > curve... what could be done would be to draw the turbine's efficiency
        > curve vs windspeed. I mean chosing a nominal RPM per windspeed that
        > would allow to get the best power without slowing the turbine down
        > nor putting it in a dangerous state (spinning too fast). Out of this
        > curve, select 10 to 20 points and then have one of these small genius
        > things such as the Logo of Siemens to divert the output to the
        > battery load and the dump load in order to always have the best load
        > vs windspeed. The Logo gets the RPM out of the generator's 3Ph
        > voltage (as its a PMG, it's linear) and checks the voltage of the
        > battery bank. Combining the two results through a simple program
        > using the Logo's internal possibilities, you can decide whether
        > you'll send 10% to the dump load at point 1, 12% at point 2 and so
        > on... or whether you wish to limit the amps (and therefore the load)
        > at low wind speeds.
        >
        > These are just ideas but it would actually be a real MPPT fo a wind
        > turbine, keeping it loaded all time long but exactly as you wish it
        > to be loaded.
        >
        > Olivier.
        >
        >


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      • Andre' Blanchard <andre@usermail.com>
        Look at how they do regen braking in the electric vehicles that use AC induction motor systems. Basically they just reduce the frequency of the inverter
        Message 3 of 3 , Feb 3, 2003
          Look at how they do "regen braking" in the electric vehicles that use AC induction motor systems. Basically they just reduce the frequency of the inverter below what the motor is spinning at, how much lower determines how much power is pulled from the motor. At the same time the inverter can/is used as a boost converter to bring the voltage up to a level that can charge the battery pack.


          Here is a copy of a message from the EVList on yahoo.
          http://autos.groups.yahoo.com/group/EVList/
          {
          Very simplified -

          Inverter still generates sine wave but watch the shaft rotation to
          maintain negative slip (generated frequency is lower than rotation).
          The AC voltage induced in the windings in return become greater than
          you put in (so after this happens you don't need to put in
          anything) and the difference is what you harvest (minus efficiency).
          Inverter switches in "reverse" mode rectifying not entire sine
          wave but part of each cycle depending on how much extra voltage
          you demand to produce. It often does it by usual PWM technique
          so "field" current is just strong enough to generate only as much
          as you want. Rectified AC charges your batteries.

          Victor

          "Patchem, Eric EM2" wrote:
          >
          > How is an AC induction motor (in the case of AC drive) used for
          > regenenerative braking? I understand how the motor works, but I cannot see
          > how it would work as a generator. I know the inverter plays a major role in
          > this, but I cannot see how an induction motor with no field connections, can
          > produce an output.
          >
          > Eric.
          }


          And here is the web page of a person on that list who sells AC motors and inverters for use in electric cars. They could likely help out.
          http://www.metricmind.com/





          --- In awea-wind-home@yahoogroups.com, "garciah" <garciah@f...> wrote:

          >> snip <<

          >
          > Now, can any one think a way that can be used to do the same thing without
          > the need of having the grid power and still be able to generate power using
          > induction motors without capacitors ?.
          >
          > I give you this thought, lets see if anyone can give an idea and solution to
          > this problem that has been in front of you for a long time.
          >
          > A challenge is presented to all of you, or like they say in Texas :You'll
          >
          > Regards
          >
          > Nando
          >
          > >
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