PWM Inverters

Discussion in 'General Electronics Chat' started by ClayJohansson, Dec 13, 2015.

  1. ClayJohansson

    Thread Starter New Member

    Dec 13, 2015
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    I have been researching AC inverters that control 3phase ac motors with a single phase input. My question is how is the third leg made up to drive the 3 phase motor? We also use a 110AC input inverter to run a 3 phase ac motor. I understand the PWM but do not understand how the additional "legs" are produced.
     
  2. Dodgydave

    Distinguished Member

    Jun 22, 2012
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    The ac is converted to dc, and an oscillator with a microcontroller produces a 3 phase output. this is varied in voltage and frequency by the micro to suit the user settings, like a Vfd.
     
  3. ClayJohansson

    Thread Starter New Member

    Dec 13, 2015
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    Thank you! So the oscillator is what makes the other leg. Is this done through a transformer?
     
  4. Dodgydave

    Distinguished Member

    Jun 22, 2012
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    No, the oscillator uses 6 mosfets in an H bridge form, two fets for each phase, to produce the sinewave output.
     
  5. ClayJohansson

    Thread Starter New Member

    Dec 13, 2015
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    Awesome! So the PWM is done with the DC bridge to change the frequency of the motor speed directed by human or electronic intervention correct?
     
  6. Dodgydave

    Distinguished Member

    Jun 22, 2012
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    Last edited: Dec 13, 2015
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