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brushless motor rectifying

Discussion in 'Electronic Design' started by Jamie Morken, Oct 5, 2007.

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  1. Jamie Morken

    Jamie Morken Guest


    If you have a wye wound brushless generator and rectify it with a 6
    diode full wave rectifier, or if you rectify it with a 3 diode half wave
    rectifier with the wye common being ground, the voltage of the 6 diode
    rectifier will be 1.77x that of the 3 diode rectifier I read, assuming
    it is a 1kW generator normally fullwave rectified is it safe to still
    extra 1kW of energy using the 3 diode rectifier configuration, or will
    the extra current required possibly overload the generator?

  2. Mook Johnson

    Mook Johnson Guest

    Probably will not work. Taking 2KW form a 1KW genertor will likely cause
  3. Jamie Morken

    Jamie Morken Guest

    Sorry I meant to say:

    is it safe to still EXTRACT 1kW of energy using the 3 diode rectifier
  4. Mook Johnson

    Mook Johnson Guest

    I don't think that can be ansewered without knowing the generator. If you
    pulling the same power with at 1/1.77 lower output voltage, the current must
    be a factor of 1.77 higher. (by 1.77) Thats ~ 3 times more I2R heating of
    the winding in the generator.

    If the generator runs cool at 1Kw with the a full wave diode bridge, it
    might be worth a shot. If it gets warm - hot to the touch. fagitaboudit.
  5. Tim Wescott

    Tim Wescott Guest

    More like 1.5 times the heating, because it'll be three times more, but at
    50% duty cycle in each coil.

    You'd want to check to make sure you don't saturate the iron, too.

    Tim Wescott
    Control systems and communications consulting

    Need to learn how to apply control theory in your embedded system?
    "Applied Control Theory for Embedded Systems" by Tim Wescott
  6. Jamie Morken

    Jamie Morken Guest

    What would saturating the iron do when running as a generator? Its not
    like a motor that would draw more current I think.

  7. colin

    colin Guest

    it has twice the current in each phase,
    but only for half the time,
    but dissipation rises with square of current,
    so the heating due to current will be double.

    if im not mistaken you should be able to draw x 1.4 the current in the 3
    diode config
    with no extra heating due to current.

    but if the windings are over specified - wich would be uneconomical -
    I cant see any other problems.

    but then diodes are a heck of a lot cheaper than replacement generators.

    if you want lower voltage can you connect it in delta config ?

    Colin =^.^=
  8. Mook Johnson

    Mook Johnson Guest

    The windings would no longer support the the BEMF since thieir inductance
    dropped and the voltage output will drop off until the coreomes out of
    saturation. Massive distortion of the output waveform as well.
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