Connect with us

Transformer query

Discussion in 'Electrical Engineering' started by BIGEYE, Aug 13, 2008.

Scroll to continue with content
  1. BIGEYE

    BIGEYE Guest

    The STEU 320/23 transformer shown here:
    http://www.block-trafo.de/fileadmin/productpdf/STEU.pdf

    is 320 kVA. As the transformer has 2 x 115 Volt outputs, can anyone tell me
    if the 320 kVA rating is 160 kVA for each output.
    If this is so, and I need 320 kVA, can I parallel up the two secondary
    outputs. Also, would you normally earth down one side of the secondary.

    TIA
     
  2. BIGEYE

    BIGEYE Guest

    Sorry, that should be VA, not kVA.
     
  3. Palindrome

    Palindrome Guest

    I rather think that you have lost a decimal point somewhere. 320kVA
    transformers tend to weigh a tad more than 4kg..

    But, yes, for that transformer, I would expect to be able to parallel
    the output windings.

    Whether one side of the secondary would be earthed is down to the
    application. That would also determine whether you really need an
    isolation transformer rather than an autotransformer - the latter should
    represent a very significant saving..

    As always, the people to ask are the manufacturer: eg
     
  4. BIGEYE

    BIGEYE Guest

    Sent an enquiry to them a couple of days ago, no reply as yet.
     
  5. john

    john Guest

    But if you do parallel them, I'd knock about 10% off the rating to allow
    In other words, one output may be slightly higher than the other, so when
    put in parallel, you would get some current, which would use up power and
    becomes heat. For this reason, it is better to get a transformer with the
    power you need and not put the outputs in parallel.

    Also make sure 2 x 115 V means there are two sets of 115V output (4 pins),
    and not 230V with a center tap (3 pins). In the later case, you cannot
    parallel the two 115V outputs. And make sure you parallel them in phase.
     
  6. Palindrome

    Palindrome Guest

    You might like to consider the situation where the one end of the two
    115v secondary windings in parallel is commoned with one of the 230v
    primary terminals and the output taken between the other terminals of
    the primary and secondary windings.

    The relative efficiency of doing that, rather than simply taking the
    output from the parallel secondary windings - I leave to those engineers
    that really understand transformer operation..
     
  7. Guest

    | The STEU 320/23 transformer shown here:
    | http://www.block-trafo.de/fileadmin/productpdf/STEU.pdf
    |
    | is 320 kVA. As the transformer has 2 x 115 Volt outputs, can anyone tell me
    | if the 320 kVA rating is 160 kVA for each output.

    This much is certain. The rating of each of the two 115V secondary windings
    is half of the total transformer rating.


    | If this is so, and I need 320 kVA, can I parallel up the two secondary
    | outputs. Also, would you normally earth down one side of the secondary.

    If there are 4 separate terminals, you most likely can. I could not find any
    wiring diagrams on the web site that would give some certainty to this answer.
    But in general, if the transformer has 2 secondary windings with the same
    voltage and current rating, they would be designed to be wired in parallel
    or series. Since the primary is 230V, the only uses for a 230V series
    connection would be to get 230V isolated, or as a 460V autotransformer.
    If that were all it was designed for, one 230V winding would do the job.
    There's little point in making a transformer with 4 secondary terminals
    for 2x115V unless they can be wired in parallel (same turns ratio) or in
    series.

    There is still the small chance they didn't do that. You need to find out from
    the manufacturer just what the wiring truly is (e.g. fully separate secondary
    windings with exactly the same number of turns).

    I've looked at a number of US transformer manufacturers, and many do show
    their winding diagrams, and some even show application wiring examples.
     
Ask a Question
Want to reply to this thread or ask your own question?
You'll need to choose a username for the site, which only take a couple of moments (here). After that, you can post your question and our members will help you out.
Electronics Point Logo
Continue to site
Quote of the day

-