3 phase bridge

Discussion in 'General Electronics Chat' started by cryosar, Nov 20, 2009.

  1. cryosar

    Thread Starter Active Member

    Apr 2, 2009
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    Dear All,
    I have attached the three phase full wave bridge rectifier circuit. I wanted to know how much voltage will appear after the rectification, if the input voltage is 230 V(L-L) & if 230V (L-N). Can anybody tel me the formula and derivation, it will be very helpful to me. Thanks in advance
     
  2. t_n_k

    AAC Fanatic!

    Mar 6, 2009
    5,448
    782
    Hi cryosar,

    Never seen that circuit before - certainly not ever as a standard 3-phase bridge. I don't think any current would flow in the neutral link even if you added a DC side load. It might be interesting to simulate the circuit.

    In a standard bridge connection one would expect the neutral either to be floating or acting as a DC side reference point - with the latter connection being the case if you wanted both a positive and negative (dual supply) output on the DC side.
     
  3. cryosar

    Thread Starter Active Member

    Apr 2, 2009
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    0
    Ok
    Can you give me the formula for the circuit without connecting neutral?
     
  4. aboamal

    Member

    May 29, 2008
    14
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    the circuit must be like this

    [​IMG]

    and the output of dc formula as following

    Vdc=Vac(3 phase)X1.3
     
  5. cryosar

    Thread Starter Active Member

    Apr 2, 2009
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    This is for 1 phase AC circuit
     
  6. cryosar

    Thread Starter Active Member

    Apr 2, 2009
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    But the measured value is not matching with the formula
     
  7. rjenkins

    AAC Fanatic!

    Nov 6, 2005
    1,015
    69
    If that circuit was used two series smoothing capacitors, with the centre point of the caps to neutral, it would give the same output whether operating on a single phase or a three phase supply.

    The output should be about double the peak of a single phase. In effect, any phase feeds two half wave rectifiers, one to positive and one to negative.

    The two diodes to neutral would prevent either smoothing cap being reverse biassed as the load discharges them after the supply is removed.


    Without the neutral link to the smoothing caps, the output should be the peak of the phase-to-phase voltage and it would work as a basic 3 phase (only) rec.
     
  8. t_n_k

    AAC Fanatic!

    Mar 6, 2009
    5,448
    782
    Just to complete this ....

    Vdc = 2.34Vs

    where Vs is the line-to-neutral voltage

    If using line-to-line voltage [VL]

    Vdc= 1.35VL
     
  9. cryosar

    Thread Starter Active Member

    Apr 2, 2009
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    The measured values are for Line to neutral voltage Vs= 49V the Vdc is 57V
    The measured values are for Line to Line voltage Vs= 49V the Vdc is 116V
     
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