How to determine primary current flow in a transformer???

Discussion in 'Homework Help' started by electronice123, Feb 17, 2010.

  1. electronice123

    Thread Starter Senior Member

    Oct 10, 2008
    What needs to be taken into account to determine the required current flow or power (VI) in the primary winding of a transformer.

    Say you just bought a transformer from a hobby store and you need to determine if the primary winding needed a load resistor, or what the current requirement is?

    What steps and or calculations do you have to do?
  2. 3ldon

    Active Member

    Jan 9, 2010
    Transformers don't need resistors.
    Generally they consume 10 watts per pound just idling at load.
  3. sgardner025

    Well-Known Member

    Nov 5, 2009
    Ideally the primary and secondary will dissipate the same power, so you can figure how much power you will be using from the secondary and do the conversion based on the ratio of the transformer.
  4. i_am_the_thorn

    New Member

    Feb 14, 2010
    you can use the approximate equivalent circuit of the transformer to calculate the Primary current.


    The rated current, and VI rating must be mentioned on the name plate..

    The ratio of the Load you are using and the VI rating multiplied by the rated current(on the secondary side) would give you the approx load current(i.e secondary)

    from that you can get the primary current by multiplying Load current with the turns ratio