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What is the total heat loss of a Liquid Filled (Insulation Class "A") Power Distribution transformer at various percentage loads ?

The total heat loss of a Liquid Filled (Insulation Class "A") Power Distribution Transformer at various loads is calculated as follows :-
 
At 100% load the total heat loss is the addition of the No Load Loss and the Load Loss
 
At X% load, the total heat loss is (X/100)² x Load Loss at 100% Load + No Load Loss
 
i.e. The No Load Loss is a constant loss and does not change with load
      The Load Loss varies to the square of the per unit load

e.g. 1000kVA transformer with a No Load Loss of 1340 Watts and a Load Loss of 12500 Watts at 100% load and reference temperature of 75ºC, has the following losses at various loads

  • 100% Load       No Load Loss = 1340 Watts      Load Loss = (100/100)² x 12500 = 12500 Watts
  • 90% Load         No Load Loss = 1340 Watts      Load Loss = (90/100)² x 12500 = 10125 Watts
  • 80% Load         No Load Loss = 1340 Watts      Load Loss = (80/100)² x 12500 = 8000 Watts
  • 70% Load         No Load Loss = 1340 Watts      Load Loss = (70/100)² x 12500 = 6125 Watts
  • 60% Load         No Load Loss = 1340 Watts      Load Loss = (60/100)² x 12500 = 4500 Watts
  • 50% Load         No Load Loss = 1340 Watts      Load Loss = (50/100)² x 12500 = 3125 Watts
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