Magnetic low voltage transformer

Discussion in 'General Electronics Chat' started by ecliptic, Sep 26, 2014.

  1. ecliptic

    Thread Starter New Member

    Sep 26, 2014
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    I've got a magnetic low voltage transformer (120V to 12V). The instruction book says that the transformer must be loaded at least 80% for proper operation. That's fine, but my mind wants to know why. I can understand overloading would be bad, but underloading? Why would too small of a load be a problem?
     
  2. wayneh

    Expert

    Sep 9, 2010
    12,094
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    Depends what "proper" means. It may need that much load to pull the voltage down to ~12V. Could be up around 16V or more, unloaded. Otherwise, I'd say the wording makes no sense.
     
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  3. MikeML

    AAC Fanatic!

    Oct 2, 2009
    5,450
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    Small wall-wart type transformers are designed to not start a fire if short-circuited (overloaded). This makes for lousy load regulation, so a unregulated DC power pack advertised as 12Vdc under rated load will shoot up to 18V unloaded...
     
  4. b1u3sf4n09

    Member

    May 23, 2014
    115
    14
    Do you have a mfr/part number for this transformer?

    If this is a split bobbin transformer with no auxiliary or safety circuitry, then I don't understand why there would be loading requirements.
     
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