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Homework Help: Transformer notation confusion?

  1. Sep 24, 2010 #1

    rock.freak667

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    1. The problem statement, all variables and given/known data

    For a transformer, I need to get the ratings on the meters (wattmeter, ammeter, voltmeter) when it is put through an open circuit test and a short circuit test.

    Primary 240/480
    Secondary 120/240

    1KVA

    60Hz

    3. The attempt at a solution

    Now I am not sure what is meant by 'Primary 240/480' and 'Secondary 120/240'. In most transformer problems, I would be told something like 6600/230 V transformer, meaning Primary = 6600 V and secondary = 230 V.

    Anyone care to guess what it means?
     
  2. jcsd
  3. Sep 24, 2010 #2

    Redbelly98

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    In the case of http://system.netsuite.com/core/media/media.nl?id=3868&c=ACCT126831&h=9037aabf87bb8934b400&_xt=.pdf" [Broken] (which I have worked with) the primary is actually two separate windings, which may be wired either in series or in parallel.

    Each winding is to get the lower voltage of the two indicated primary specifications; when wired in series, the series combination would then get twice this voltage, or the higher primary specification.

    Similarly, the secondary consists of two separate windings which may be combined either in series or in parallel.

    If this is the case for your transformer, you should have 4 input wires and 4 output wires.
     
    Last edited by a moderator: May 4, 2017
  4. Sep 25, 2010 #3

    rock.freak667

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    That sort of confuses me more, as then it seems as if the 240/480 side is itself like a transformer with a primary side of 240V and a secondary side of 480 V?

    If that is the case, then there is no need to really consider the 240 V?

    Otherwise, I am not sure how I would get the ratings for the OC and SC tests with the configuration.
     
  5. Sep 25, 2010 #4

    Redbelly98

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    No, the primary side consists of two coils with equal numbers of turns. The purpose of having two coils is that the transformer could be used with two different input voltages. Did you see the schematic at the lower left of the .pdf file I linked to before? If the input is the higher voltage, the primary coils should be wired in series; if the input is the lower voltage, they get wired in parallel.

    How many wires are coming out of your transformer? If my explanation was correct, there should be 8 wires.
     
  6. Sep 25, 2010 #5

    rock.freak667

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    I understand a bit better now.

    Well you see right, I don't have a picture of the transformer per se. It is sort of a lab thing I have to do and I was asked to give the ratings. The most I can get is the schematic of how the usual transformer looks during the OC and SC tests, not with the two coils in series/parallel.


    EDIT: So that means I don't really need to bother about the two voltages and just use the transformer as if it were specified as 480 (primary) and 240 (secondary)?
     
    Last edited: Sep 25, 2010
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