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DF Load for Transformer

  1. Oct 15, 2015 #1
    I have seen an excel sheet in calculator to calculate the size of transformer.
    There are option to put the vales of Kw,PF,Qty and Equipment D.F.
    I could not understand what is D.F.
    What is the equation to calculate the D.F and equation to calculate the total load D.F?
  2. jcsd
  3. Oct 15, 2015 #2


    Staff: Mentor

  4. Oct 15, 2015 #3


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    Education Advisor
    Gold Member

    D.F. likely means equipment Demand Factor. If the equipment is a stove or Washing and Drying machines in an apartment complex that furnishes these appliances, they would generally not all run at the same time. The NEC (National Electric Code) provides tables that allow you to reduce the size of the service transformer instead of calculating with all the equipment at 100%.
  5. Oct 15, 2015 #4
  6. Oct 15, 2015 #5
    I would have assumed derating factor. This would be a fudge factor thrown in where equipment spec is derated. Usually by around 20% as a rule of thumb.
  7. Oct 15, 2015 #6
    I didn't see fudge factor in the spec.
    Can anyone help me to calculate the D.F load?
  8. Oct 15, 2015 #7
  9. Oct 15, 2015 #8
    Please See the below screen shot. Find the highlighted area
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