Speed control of 3 phase induction motor

Discussion in 'The Projects Forum' started by han, Oct 25, 2007.

  1. han

    Thread Starter New Member

    Oct 25, 2007
    5
    0
    hi guys,im new to tis forum
    currently im doin a project bout design a cicuit to control the speed of a 3 phase induction motor, i already hav the inverter circuit, but im having a problem to get the firing circuit.do anyone have a sample for this?really thank you if can give me a hand here...
     
  2. Sebi

    Well-Known Member

    Sep 24, 2005
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  3. han

    Thread Starter New Member

    Oct 25, 2007
    5
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    thankz,but im doing a manually speed control circuit..is there any simple circuit that doesn't require any pic or plc?thankz lot for da help
     
  4. beenthere

    Retired Moderator

    Apr 20, 2004
    15,815
    282
    I don't think a three phase waveform can be controlled manually. You have to alter frequency to control speed.
     
  5. han

    Thread Starter New Member

    Oct 25, 2007
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    then how do i alter the frequency?
     
  6. recca02

    Senior Member

    Apr 2, 2007
    1,211
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    by increasing the firing rate of the inverter components.
    usually mosfet's or IGBT's
     
  7. han

    Thread Starter New Member

    Oct 25, 2007
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    in the inverter circuit i have 6 IGBT s, but how do i control the firing rate?
     
  8. beenthere

    Retired Moderator

    Apr 20, 2004
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    As above: use a microprocessor. Look up "induction motor speed control" on Google.
     
  9. han

    Thread Starter New Member

    Oct 25, 2007
    5
    0
    oh.means to control the speed of an induction motor we still need a microprocessor la?theres no other way?
     
  10. thingmaker3

    Retired Moderator

    May 16, 2005
    5,072
    6
    Of course there are other ways. But they are far more complicated and less reliable than using a microprocessor. You could, for example, gang together a control to simultaneously vary both motor supply voltage and the frequency from a VCO. It would be quite challenging to design and adjust, though. You would have to do a lot more soldering, too. In the long run, it would probably be more expensive as well. And less reliable. But you could do it.
     
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