Current rating for a transformer

Discussion in 'General Electronics Chat' started by kdillinger, Oct 11, 2009.

  1. kdillinger

    Thread Starter Active Member

    Jul 26, 2009
    141
    3
    I have a stupid question about transformers. I am working on another project that interfaces a power amplifier to the electrical mains via a transformer.
    I am researching Google and looking back through my old books to find a current rating or something that is equivalent. So far there are failures and not much else is known at the moment.
    The transformer the other team is using is "rated at 200mA" and the power amplifier in the application can deliver 2A.
    This immediately seems to be the problem, but I am a transformer neophyte and have no idea of there is a current rating similar to a resistor. Any tips while I am researching?

    -Ken
     
  2. GetDeviceInfo

    Senior Member

    Jun 7, 2009
    1,571
    230
    Most suppliers of smaller transformers will report thier secondary current. Transformers will be rated in VA, or Volt Amps. You divide this by your secondary voltage to arrive at it's current capabilities.
     
  3. kdillinger

    Thread Starter Active Member

    Jul 26, 2009
    141
    3
    That makes perfect sense and probably the issue. I will have to ask them for the datasheet. Thanks.

    -Ken
     
  4. bountyhunter

    Well-Known Member

    Sep 7, 2009
    2,498
    507
    Small transformers have a secondary rating given in in RMS Volts and RMS current. They are specified assuming a resistive load, although that is rarely how they are used. BTW: transformer RMS current is always much higher than DC load current following a rectifier/capacitor: if you use a full wave bridge rectifier, transformer current is about 1.8X DC load current.
     
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