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Thread: 240 volt to 480 volt transformer

  1. #1
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    240 volt to 480 volt transformer

    I want to step 240 single phase to 480 volt 3 phase. I understand I can wire a transformer in reverse to achieve this. Can the transformer convert to 3 phase power or do I need a phase converter on secondary? I need a neutral so transformer will be a wye and not sure what kva I'll need yet. I deal with mostly residential and don't have alot of experience with transformers. Any good websites referencing transformers? Thanks

  2. #2
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    Quote Originally Posted by Ken 6789 View Post
    I want to step 240 single phase to 480 volt 3 phase. I understand I can wire a transformer in reverse to achieve this. Can the transformer convert to 3 phase power or do I need a phase converter on secondary? I need a neutral so transformer will be a wye and not sure what kva I'll need yet. I deal with mostly residential and don't have alot of experience with transformers. Any good websites referencing transformers? Thanks
    If you need 480Y/277, you will need to purchase a step-up transformer, running a step-down unit in reverse will not provide you with the neutral connection.

    If you need 3-phase from single-phase you will need some typ of phase convertor.
    Just because you can, doesn't mean you should.

  3. #3
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    Quote Originally Posted by Ken 6789 View Post
    I want to step 240 single phase to 480 volt 3 phase. I understand I can wire a transformer in reverse to achieve this. Can the transformer convert to 3 phase power or do I need a phase converter on secondary? I need a neutral so transformer will be a wye and not sure what kva I'll need yet. I deal with mostly residential and don't have alot of experience with transformers. Any good websites referencing transformers? Thanks
    You can check out Federal Pacific and Hammond website. They both have info on transformer basics. Hope this helps.
    Whatsoever thy hand findeth to do, do it with thy might - Ecclesiastes

  4. #4
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    1 phase transformers are available to step up voltage from 240 to 277 volts.
    Sola/Heavy duty HS12F series for example.
    If 480 v, 3 phase is required for motors an inverter will be needed.
    The question does not indicate what 480/277 is being used for.
    If 277 volt is the only voltage needed, usually lighting, then an inverter is not needed.
    Simple use a 1 phase transformer to step up the voltage to 277.

    BILLY

  5. #5
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    I have use Rotary Phase Convertors from Rotadyne many times with good luck.

    http://www.willett.ca/RotaDyne.htm




    Derek

  6. #6
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    Ken, tell us more about the loads; not just size, but types and quantities.

    Keep in mind that you'll need more kva at 240v than you'll get at 480v.
    Code references based on 2005 NEC
    Larry B. Fine
    Master Electrician
    Electrical Contractor
    Richmond, VA

  7. #7
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    Neighbor of mine is considering purchasing the Nissan Leaf, all electric car. There are 3 options for charging: 120 volt, 20 hours to charge; 240 volt, 7 hours to charge; 480 volt, 30 min charge @80%. He wants to see if 480 volt power is possible in his garage, which I told him no house has 480 service and step-up transformer is required and not cost-effective. I tried to convince him to wire at 240 volt, but he wants to recharge car in shortest time possible. Also, I told him the expense and a higher electric bill, but still insists on shortest recharge time. I am not 100% sure if charger is 3 phase yet or amperage requirements. I know at 240 single phase, the spec calls for 40 amp ocp. Thanks for replies.
    Last edited by Ken 6789; 12-07-10 at 11:54 PM.

  8. #8
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    From what I have read there are very few 480 volt chargers currently produced and they cost about $40,000. I believe they require a 125 amp 3 phase circuit. These chargers are designed for commercial applications not residential.
    Curt Swartz
    Electrical Contractor

  9. #9
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    Quote Originally Posted by LarryFine View Post
    Ken, tell us more about the loads; not just size, but types and quantities.

    Keep in mind that you'll need more kva at 240v than you'll get at 480v.
    Dont you mean - You will need more amps at 240 to get the same Kva at 480.


    Quote Originally Posted by Ken 6789 View Post
    Neighbor of mine is considering purchasing the Nissan Leaf, all electric car. There are 3 options for charging: 120 volt, 20 hours to charge; 240 volt, 7 hours to charge; 480 volt, 30 min charge @80%. He wants to see if 480 volt power is possible in his garage, which I told him no house has 480 service and step-up transformer is required and not cost-effective. I tried to convince him to wire at 240 volt, but he wants to recharge car in shortest time possible. Also, I told him the expense and a higher electric bill, but still insists on shortest recharge time. I am not 100% sure if charger is 3 phase yet or amperage requirements. I know at 240 single phase, the spec calls for 40 amp ocp. Thanks for replies.
    The first thing you really need to know is what VA is needed. You may be able to charge it faster @480 volts but what if after transforming voltage and possibly going through phase conversion you need about 80 amps @ 240 volts single phase and his house only has a 100 amp panel? (The 480 volt 3 phase would draw about 23 amps per phase in this case)

    Electric bill will not be any higher - it will take the same kWhrs to charge the battery to the same level (ignoring losses which should be minimal) no matter what the source is. You pay for Kwhrs not amps.

  10. #10
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    Nov 2007
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    If 480 volt charger is approx $40,000 then I'm sure I'll be able to convince him to stick with 240. Thanks for the replies!

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