operation of 3 phase inverter

Discussion in 'Electronics Resources' started by diya khan, Dec 20, 2011.

  1. diya khan

    Thread Starter New Member

    Nov 29, 2010
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    hey guys...


    i want to know the operation of single phase and 3 phase inverter...please provide me links or books.. or jounals...anything is appreiciatedd

    thank u soo much:)
     
  2. strantor

    AAC Fanatic!

    Oct 3, 2010
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    what kind of inverter? an inverter for powering electronic devices/appliances (like the kind you plug into a cigarette lighter and power your laptop) or a VFD (aka inverter) for controlling motors?
     
  3. diya khan

    Thread Starter New Member

    Nov 29, 2010
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    oppzz sry i frgt to mention, yes its a VFD for controlling motors!
     
  4. strantor

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  5. diya khan

    Thread Starter New Member

    Nov 29, 2010
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    i have already gone through this, bt it doesnt say about the operation of a three phase inverter=/
     
  6. strantor

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    The 3 phase inverter has a rectifier stage: incoming power, can be single phase for smaller VFDs, but usually 3 phase, is rectified into DC. The DC is filtered and stored in a capacitor bank.
    From here it goes to the inverter bridge. The inverter bridge consists of 6 semiconductor switches, usually IGBTs, which are 3 sets of 2switches. the 3 points between the 3 sets of switches are the points where your motor connects. the way it works is, that one switch on the top closes and one switch on the bottom closes simulaneuosly (never 2 switches in the same set) and this will allow current to flow through one of the 3 windings.
    When I say that these switches "close" - I do not mean that they close and stay closed. I mean that they pulse - it's called PWM - the duration of the pulse ON time determines how much current is allowed to flow through the winding. the frequency of this PWM is in the kiloherts range.
    Now, there is a microcontroller inside which will determine how fast to cycle the commutation frequency (ex. 0-60hz) and the voltage (via PWM) based either from operator input (potentiometer or PLC) or internal PID algorithms.
     
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  7. diya khan

    Thread Starter New Member

    Nov 29, 2010
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    thank you!

    is sumthing to do with harmonics? im sorry but my knowledge on this is very poor=/
    my lecturer had asked me that why would the 3rd harmonic be reomoved? is it symthing to do with pwm?

    my basics are soo poor!

    =(
     
  8. strantor

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  9. thatoneguy

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    Feb 19, 2009
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    Click How Drive Changes Motor Speed at the bottom of page for more detail.
     
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