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Voltage aiding transformer.

Discussion in 'Electronic Basics' started by Terry, Oct 2, 2003.

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  1. Terry

    Terry Guest

    Anybody have any experience/advice concerning a proposed 'voltage
    aiding' transformer set up.

    Namely a 115 to 230 volt (1:2 step up with completely separate
    primary and secondary windings; not an auto transformer).

    Input 115 volts with secondary 230 volts 'added' to produce an
    output of 345 volts to power three 347 volt commercial
    fluorescent light fixtures. Each fixture equipped with two 60
    watt 96 inch tubes, a total of six 60 watt tubes plus ballast
    transformer inefficiencies and possible power factor.

    My figuring says that the transformer will have to up voltage
    from 115 to 230 and be capable of handling two thirds of the
    total wattage (VA), approximately. Also that it's secondary
    winding must be able to carry the total input current since that
    will flow through both windings in the 'series voltage aiding'

    Several primary/secondary transformers available; one, typically
    is rated 340 VA, 115 to 230 volts.
    Also have an a centre tapped auto transformer 0-115-230 available
    but haven't figured out a way to use that in a voltage aiding
    situation; at least with a suitable and conventional zero
    potential neutral connection to the fixtures, also it would
    require 230 volts (which is available) and double pole switching
    of that 230 volt input which would like to avoid.

    Would anyone like to push a pencil around and recommend ideas or
    problems? Any suggestions ranging from "Crazy idea" to practical
    considerations welcomed. When weather gets wintry intend to 'test
    bench' this idea and possibly build into workshop; I've got scads
    of spare 96 inch light tubes, more than we'll ever need, a spare
    347 volt ballast; the fixtures were free and will provide 24 feet
    of lighting, ideal for our 44 foot long workshop along with other
    spot lighting over specific items.

    Thanks for any input. Terry.
  2. John Fields

    John Fields Guest

    When you're finished it'll be an autotransformer, and here's how to do

    | |
    115HOT>--+-- || --+
    NEUT>----+-- || -------->345HOT
  3. My figuring agrees.
    The center tapped autotransformer is really a 120 to 120 transformer
    with the primary and secondary connected in series, much like you want
    ot do with a 120 to 240 volt transformer. The only ways to get 360
    volts out of it is to connect it as you say, across half of a 230 volt
    circuit boosting that to 240, and adding the other half of the 240 in
    series. So you are correct that it would take a double pole switch to
    operate it, but would allow a smaller transformer.
  4. Terry

    Terry Guest

    John Popelish and John Fields replied, thanks both for confirming
    my various configurations. Wanted to make sure I hadn't missed
    something obvious.

    For example John Popelish said;
    Yes transformer, with 230 volt input to circuit, would handle
    about one third of the wattage plus losses & PF etc. And would
    need double pole switch to open both sides (legs) of the 230
    volts input.

    I'd like to have a two wire 115 volt input with conventional
    (white wire in North America) unswitched neutral and a single
    pole switch in the live 115 volt (black in North America) lead.
    I'll probably use red or a other colour for the live 345 volt
    output lead. Mounting the whole voltage step up arrangement in a
    grounded/earthed metal box with warning sign and circuit
    description on outside; cos the next person to work on it, even
    if an electrician, won't be expecting 345 volts in a residential
    situation! May even put say a 5 amp fuse in the input to the
    transformer and/or wire it from an individual 115 volt 15 amp
    breaker in the panel. Since the transformers I have are rated for
    230 volts etc. and were likely factory tested to higher voltages
    I don't expect insulation to frame/ground to be a problem even
    though transformer/s old.

    Many thanks for input and comments. Terry.
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