3 phase AC to Single phase AC converter

Discussion in 'General Electronics Chat' started by vks_foe, Jun 24, 2014.

  1. vks_foe

    Thread Starter Active Member

    Jan 11, 2009
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    I need a three phase AC to single phase AC, 50 Hz converter of 15-20kVA rating with sine wave output. I couldn't find it readily available in market nor could get good response in google.. Are such converters available ? Pls suggest.
     
  2. inwo

    Well-Known Member

    Nov 7, 2013
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    What type of load?

    Most single phase loads can be balanced across 3 phases.
     
  3. BR-549

    Well-Known Member

    Sep 22, 2013
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    May we know what you are powering with the single phase? What is the voltage of the 3 phase input? What voltage are you looking for in the single phase output?
     
  4. MaxHeadRoom

    Expert

    Jul 18, 2013
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    2,373
    A 3ph transformer is made up of three single phase transformers.
    Why not just install a suitable sized 1ph Txfmr across two of the incoming phases?
    What are you feeding it from?
    Max.
     
  5. MrAl

    Well-Known Member

    Jun 17, 2014
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    Hi,

    Wow, 20kW from single phase is a lot of current. Even at 220vac that's around 91 amperes. That's why 3 phase works better for huge loads like that.
     
  6. tcmtech

    Well-Known Member

    Nov 4, 2013
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    I suggest reading up on 'Zig Zag' or 'Z' connected systems. They are the easiest way to get a large single phase load to balance out over a three phase feed source.

    Personally I don't consider 20 KW on single phase top be all that big. The primary feeder for my place is a 200 amp 120/240 single phase.
     
    MaxHeadRoom likes this.
  7. DNA Robotics

    Member

    Jun 13, 2014
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    26
    Just use 2 of the 3 wires and you will have single phase.
     
  8. MrAl

    Well-Known Member

    Jun 17, 2014
    2,433
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    Hi,

    Are you telling me that you would not mind loading your 120vac line with 20kW from one single application device? That's 167 amperes, assuming it is a purely resistive load. If it's not purely resistive, it could be much worse.

    Also, connecting to one phase of a three phase system could cause a big imbalance in the three phase system.

    When is the last time you ran something this huge :)
     
  9. alfacliff

    Well-Known Member

    Dec 13, 2013
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    wouldnt it be advisable to find out if the 3 phase is delta or wye connected?
     
    Last edited: Jun 25, 2014
  10. MaxHeadRoom

    Expert

    Jul 18, 2013
    10,548
    2,373
    I also have a 1ph 50kVA transformer sitting at the end of my yard feeding a 200amp service to the house and shop, apart from the usual domestic load, I also have a small machine shop with CNC machines and a 50amp outlet for a welder.
    The OP did not mention if this was for a singular load, as he is posting from India the normal domestic supply is 220v.
    Max.
     
  11. tcmtech

    Well-Known Member

    Nov 4, 2013
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    Well my big plasma cutter pulls around 135 amps at 240 VAC plus I have a 15 HP air compressor that cycles on and draws 100 - 120 amps on start up along with all my normal home and shop background loads. So yes for me seeing 40+KW/KVA or higher loads at my place is trivial at best.

    Personally around here seeing newer farms and larger rural homes with 400 and 600 amp 120/240 VAC services is pretty normal here.

    A buddy of mine built a new shop a few years ago with all electric heating on top of his all electric heat in his house so his service was upgraded to a 600 amp system with a 100 KVA transformer feeding his place.
     
  12. MrAl

    Well-Known Member

    Jun 17, 2014
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    Hi,

    Wow that's amazing. Here we are lucky if we have 200 amp service, and that's when it works right.

    Factories around here of course have better.
     
  13. inwo

    Well-Known Member

    Nov 7, 2013
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    200 amps was enough for me when I build my home, but 40 circuits is never enough.

    So I went to 400A rather than a sub-panel.
     
  14. vks_foe

    Thread Starter Active Member

    Jan 11, 2009
    55
    5
    Pls explain. I have only one load which is single phase 15kva..
     
  15. vks_foe

    Thread Starter Active Member

    Jan 11, 2009
    55
    5
    It is an inductive load with pf >0.9. Input : 415 ph-ph. o/p : i need variable ac (0-1250V, 50Hz)
     
  16. vks_foe

    Thread Starter Active Member

    Jan 11, 2009
    55
    5
    This is what I was worried about. I donot want to create an imbalance in the system. So i thought of buying a solid state converter which has 3 phase 415V ac input and single phase AC output which is variable.

    BTW, how much load imbalance is generally allowed, I mean if i'm loading a phase with 15kVA, what should be the minimum rating of the feeding transformer that this becomes negligible (or acceptable)?
     
  17. tcmtech

    Well-Known Member

    Nov 4, 2013
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    Personally I would not worry about phase imbalance unless you are running at over 50% of what the primary three phase supply transformer is rated for phase to phase for extended periods.
    Which if its a utility owned and operated unit supplying power to multiple customers or the like the odds are its pretty robustly built and even that much of a imbalance is not likely going to cause any substantial problems on the other lines.

    15 KVA may sound like a lot to you but on the utility scale of things its trivial at best.
     
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