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three phase rectifier voltage issue

Discussion in 'Power Electronics' started by alal, Jun 21, 2019.

  1. alal

    alal

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    0
    Jun 21, 2019
    I captured an output voltage waveform of the three-phase rectifier system. Could anyone help me understand what might be the cause of the little spikes?

    upload_2019-6-21_15-2-21.png
     
  2. Minder

    Minder

    2,807
    583
    Apr 24, 2015
    Is this supplying any load, or just a 3ph rectifier?
    What is the source of the 3ph?
    Where are you referencing it to, the wave form is not a normal rectified pattern for 3phase.
    The should have a 120deg overlap for every cycle.
    M.
     
    Last edited: Jun 21, 2019
  3. alal

    alal

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    0
    Jun 21, 2019
    It has dc crane and dc led lights on the system. The crane load is on and off. When the led lights are on, the problem exaggerates. I'm trying to figure out the source of the problem, the rectifier or the led driver. The source of the 3ph is from a three-phase ac transformer.
     
  4. Minder

    Minder

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    583
    Apr 24, 2015
    I added a edit in the mean time, as I said the wave form does not look normal other than the spike.
    M.
     
  5. Minder

    Minder

    2,807
    583
    Apr 24, 2015
    It appears to be more 1phase than a typical 3 phase output.
    M.
     
  6. alal

    alal

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    0
    Jun 21, 2019
    I think the correct waveform should look like this. It seems it's missing every other peak.
    upload_2019-6-21_16-35-46.png
     
  7. Minder

    Minder

    2,807
    583
    Apr 24, 2015
    You should be getting a 360deg approx 5% ripple sitting on the top.
    What is the nature of the rectifier and where is your reference point from?
    M.
     
  8. alal

    alal

    6
    0
    Jun 21, 2019
    The time division is 7.95 on the x-axis. I counted the peaks based on this time.
     
  9. Alec_t

    Alec_t

    2,617
    692
    Jul 7, 2015
    Are you sure the polarities of all the rectifier diodes are correct?
     
  10. alal

    alal

    6
    0
    Jun 21, 2019
    I think the polarities are correct. I run a simulation with the wrong polarity, the waveform does not look like the measured.
     
  11. alal

    alal

    6
    0
    Jun 21, 2019
    I found out it is actually half controlled rectifier, so 3 diodes, 3 SCRs. The waveform is normal.
     
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