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Transformer efficiency

  1. Mar 25, 2016 #1
    hello there
    i have some confusion about transformer efficiency
    when it is max?
    and how it is calculated in different loading conditions e.g. at 80% of full load or at given PF
  2. jcsd
  3. Mar 25, 2016 #2


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    Staff: Mentor

    What reading have you been doing about this so far? Can you post links to what you have been reading?

    And what kind of transformers are you asking about. High voltage, high power transmission line transformers in power distribution systems? 50/60Hz power transformers in appliances? High frequency DC-DC switching power supply transformers?
  4. Mar 26, 2016 #3


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    Science Advisor

    That confusion is not surprising.

    Thicker wire has less resistive losses, but then needs to be longer and fills more aperture in the core. The core path length is then greater so weight of core is greater. You might think that heavier transformers are more efficient, but they actually cost more up front and need greater magnetising current, even when operating idle.

    For fixed frequency operation the material and cross section of the magnetic path is a critical parameter that determines the current limit due to saturation. A good rule of thumb is that when operating, the temperature of the magnetic core should be similar to the temperature of the conductive windings. Both those temperatures can be reduced by spending more money up front, but the economics are optimised when heat generation is similar in each.
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