Induction motor off grid generator. ideas & questions

Discussion in 'Power Electronics' started by FunExhibits, Mar 4, 2017.

  1. FunExhibits

    Thread Starter New Member

    Mar 4, 2017
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    I wonder if the capacitor in a PSC induction motor could be swapped for a choke coil inductor instead?
    Would shifting the phase of the auxillary coil current to be lagging the main coil instead of leading still achieve a rotating field?
    Would it cause this motor to rotate in opposite direction?
    Isn’t phase shifting auxillary coil current by adding an inductive choke identical to the function of a shaded pole motor? That fat wire single turn shading coil is an auxillary winding. And instead of phase shift via surging external capacitor, the shading coil’s phase shift is achieved through inductance as its own short circuit current lags main coil current.
    I think adding a choke coil in place of the capacitor will work but it will increase var (VoltAmpReactive power).
    Is var real current surging in the motor coils? Does this "apparent power" cause real waste heat inside the motor?

    Could using this inefficient inductive phase shift technique have some advantage when trying to use a PSC induction motor as an off-grid generator?
    If generated AC frequency is allowed to vary, can an off grid single phase induction motor deliver power at a wider range of speeds by varying the capacitance to match the load? Or perhaps using a variable inductance to keep the field currents flowing ? Would a triac be useful to tune behavior of this type of off-grid inductive generator?
     
  2. MaxHeadRoom

    Expert

    Jul 18, 2013
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    I assume these are purely academic questions as in just about all cases they do not have much, if any practical merit.
    Max.
     
  3. FunExhibits

    Thread Starter New Member

    Mar 4, 2017
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    Hi Max,
    Thanks for your reply and for consistently sharing valuable insights on this site.:)
    Yeah, I hope that my curiosity driven questions will deepen my understanding about electric motors and AC circuits.
    One of my goals is to develop a fun project for kids to hack box fans into windmill generators which require no fabrication skills.

    Couldn't an Arduino controller continuously tune the phase shift and modulate the loading of a wind powered box fan induction generator so it delivers some power over a wide range of speeds without grid connection?
    Thanks for considering my questions.
    Michael Flynn
     
  4. MaxHeadRoom

    Expert

    Jul 18, 2013
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    It may be easier to use a P.M. motor such as the small dc motors out of toys etc to demonstrate the generator effect.
    Max.
     
  5. FunExhibits

    Thread Starter New Member

    Mar 4, 2017
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    I am drawn to the usefully sized fan blade and ubiquitous nature of trash picked box fans.
    I'm also interested in the underlying physics- even if this only amounts to a thought experiment.
    I predict swapping an inductive choke coil in place of the capacitor in PSC fan will reverse rotation and cause wasteful var heating.
    Does that make sense?
    Thanks,
    Michael Flynn
     
  6. tcmtech

    Distinguished Member

    Nov 4, 2013
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    It's all academic and has very little rational let alone practical application in real world working conditions especially those that would be found in any common box fan motor. Split capacitor or shaded pole in base design.

    If you want to show kids how to turn box fan motors into generators show them how to use a drill, epoxy to attach neodymium magnets to the rotor to make the motor into a simple permanent magnet AC generator.
     
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