converters

Discussion in 'General Electronics Chat' started by hakim_789, Feb 17, 2015.

  1. hakim_789

    Thread Starter New Member

    Feb 17, 2015
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    Hi friends,
    I am looking for rough idea how to convert 3 phase ac to dc . please help
     
  2. Shabbir_Ahmed

    New Member

    Feb 17, 2015
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  3. Kermit2

    AAC Fanatic!

    Feb 5, 2010
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    first thought i have is standard rectification with diodes. is there some reason you cannot do it thst way?
     
  4. Dodgydave

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    Jun 22, 2012
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  5. hakim_789

    Thread Starter New Member

    Feb 17, 2015
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    Actually I want to convert 3 phase AC (which is about 415V here) and give the output to a dc motor. Is it better to use diodes or thyristors in this case ?
     
  6. hakim_789

    Thread Starter New Member

    Feb 17, 2015
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    Thank you Shabbir_Ahmed , Dodgydave and Kermit2 for your response
     
  7. Dodgydave

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    Jun 22, 2012
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    If you want to vary the speed , then use thyristors,you can buy a dedicated ready made one cheaper.
     
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  8. hakim_789

    Thread Starter New Member

    Feb 17, 2015
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    Thanks. Is there any simple (cheap) way to reduce or remove the ripples in the output. Is a filter practical in this case??
     
  9. Dodgydave

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    Is there a reason why you're not using an AC motor?
     
  10. hakim_789

    Thread Starter New Member

    Feb 17, 2015
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    Actually I am using the dc motor to test the response for RLE load. I wanted a way to remove ripples so that I won't screw up the dc motor.
     
  11. Kermit2

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    the ripple will bother you more than the motor. they are tough and work with disgustingly noisy, poorly shaped and unfiltered power. application should tell us more about what kind of filtering yout motor truly needs
     
  12. WBahn

    Moderator

    Mar 31, 2012
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    The motor itself makes a pretty good filter. That's one of the reasons that PWM waveforms can be used so successfully with DC motors.
     
    Last edited: Feb 17, 2015
  13. MaxHeadRoom

    Expert

    Jul 18, 2013
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    3 phase SCR full-wave bridges have been used for decades for DC servo control, you do not need ripple removal with 3ph due to the low percentage ripple level compared to 1ph.
    Max.
     
  14. crutschow

    Expert

    Mar 14, 2008
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    The unfiltered output voltage ripple from a 3-phase full-wave bridge is <5% so should not affect the operation of a DC motor, as Max noted.
     
  15. #12

    Expert

    Nov 30, 2010
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    I think it would be good to use an electrician because that amount of power is incredibly dangerous. You have to go, "Full Safety Practices" because you might not survive even one mistake.
     
  16. WBahn

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    I fully concur -- if you are asking the kinds of questions you are asking, then there is a REAL good probability that you really don't have the level of knowledge and experience to safely work with these kinds of systems unsupervised. So pay the money to get someone that can supervise and educate you about these systems -- the cost is minimal compared to the cost of getting tangled up with this kind of power, even if the only result is damaging some equipment.
     
  17. ian field

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    Oct 27, 2012
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    For only rectification; 6 diodes will do fine, you can replace 3 of the diodes with thyristors if you want to control the output.
     
  18. GopherT

    AAC Fanatic!

    Nov 23, 2012
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    This is slightly higher voltage but the same effect can be imagined with 415 vs. the 480 3-phase here. I have a screw driver in my maintenance dept that was dropped across some similar power sources - not much left. A small slip of a screw driver, or a poorly tightened lug can cause some major damage in a fraction of a second. By damage, I don't mean the building.

     
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  19. #12

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    Nov 30, 2010
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    In my first experience with 440V 3 phase, one leg of the disconnect didn't disconnect. I'm lucky I only lost my screwdriver!
     
  20. Kermit2

    AAC Fanatic!

    Feb 5, 2010
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    found the remnants of a squirrel(fuzzy tailed rat) under a transformer pole. 14.4 kV! it looked sorta of squirrel like still, but up close it was just a piece of black charcoal. a very un-natural end for the rat with a pretty tail.
     
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