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smallest transformer

Discussion in 'Electrical Engineering' started by [email protected], Apr 28, 2007.

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  1. Guest

    What is about the smallest size (in terms of physical dimensions) that a
    transformer could be made suitable to step 7200 volts down to 240 volts
    in utility grade service, including any cooling parts as might be needed?
    Assume a very small load is all that needs to be powered, such as 50 VA
    or less. I'm presuming the necessary primary insulation is going to be
    the major factor limiting how small this can get. The secondary needs to
    be grounded, so floating service is not an option (and hence voltage to
    the enclosing case is an issue).
     
  2. JohnR66

    JohnR66 Guest

    I would assume such a transformer would be around the size of a television's
    horizontal output transformer. A bit bigger and heavier because of the
    frequency of the power being converted. Only 50VA would not require any
    special cooling system. You didn't mean 50KVA did you?
    John
     
  3. SuperM

    SuperM Guest


    Actually, things like creepage distances and what not will likely be.

    Input leads will need to be fed through teflon tubes or the like.

    You could step down your source, then feed your final transformer in a
    two stage scenario as well. That will reduce problems a bit.
     
  4. Look for information on metering PT (potential transformers). They are
    usually capable of a 100VA or so. As far as I know, they are the smallest
    commerically available transformers to do what you want. They are solid (no
    oil) and need no cooling. As for the actual dimensions, I hate to hazard a
    guess. The bushings are the largest part.

    Charles Perry P.E.
     
  5. Guest

    | I would assume such a transformer would be around the size of a television's
    | horizontal output transformer. A bit bigger and heavier because of the
    | frequency of the power being converted. Only 50VA would not require any
    | special cooling system. You didn't mean 50KVA did you?

    No, I did not mean 50kVA, just 50VA ... enough to power a small light.

    But a 7200->240 one would be larger than a 120->12 one.
     
  6. Guest

    | On 28 Apr 2007 21:06:59 GMT, Gave us:
    |
    |> I'm presuming the necessary primary insulation is going to be
    |>the major factor limiting how small this can get.
    |
    |
    | Actually, things like creepage distances and what not will likely be.
    |
    | Input leads will need to be fed through teflon tubes or the like.
    |
    | You could step down your source, then feed your final transformer in a
    | two stage scenario as well. That will reduce problems a bit.

    The combined size would have to be considered in a two stage scenario.
     
  7. Guest

    | Look for information on metering PT (potential transformers). They are
    | usually capable of a 100VA or so. As far as I know, they are the smallest
    | commerically available transformers to do what you want. They are solid (no
    | oil) and need no cooling. As for the actual dimensions, I hate to hazard a
    | guess. The bushings are the largest part.

    Could the bushings be smaller if the entire transformer case were of
    some appropriate non-conductive material?
     
  8. SuperM

    SuperM Guest


    Of course.
     
  9. The entire transformer is usually rubber for a 15kV class metering PT.

    Charles Perry P.E.
     
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