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Homework Help: Transformers Current and Voltage

  1. Apr 30, 2015 #1
    1. The problem statement, all variables and given/known data
    A transformer has a turns ratio of 5 : 1. It is connected to a 230 V supply and an output (secondary) current of 2.7 A is measured. If the transformer is 90% efficient, calculate:
    1. Secondary voltage
    2. Input (primary) current

    2. Relevant equations

    3. The attempt at a solution
    I dont think it can be solved as most of the equations dealing with transformers assume an ideal transformer.
  2. jcsd
  3. Apr 30, 2015 #2
    Hi Xvivi,
    The ratio is 5:1, just to remind that even the tronsformer isn't 100% efficient the output is yet the same, the only thing that changes is the ouput current,
    You can pull out the ouput voltage, use the fact of thethe 90% efficiency to determine the input current, good luck !
  4. May 2, 2015 #3


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    Staff: Mentor

    In your analysis here you do include an ideal transformer, then add an external resistance to it to account for its non-ideality.
  5. May 2, 2015 #4


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    Science Advisor
    Homework Helper
    Gold Member

    Work out the secondary voltage assuming an ideal transformer.
    Work out the output power
    Work out the input power allowing for the efficiency being 90%
    Work out the input current.
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