ELECTRICAL ENGINEERING SUBJECT- DC MACHINE Year/Sem- 2ND year /4th sem Date-15/04/2020 UNIT-3 Time: 10.30-11.20 TRANSFORMERS Maximum Effieify Coiditoi of a Traisformer The effienfy of the transformer alon with the loa" an" the wower faftor is erwresse" y the iven relaton: The value of the terminal volta e V2 is awwrorimately fonstant. Thus, for a iven wower faftor the Transformer effienfy "ewen"s uwon the loa" furrent I2. In equaton (1), the numerator is fonstant an" the transformer effienfy will e marimum if the "enominator with resweft to the varia le I2 is equate" to zero. i.e Cowwer losses = Iron losses Thus, the transformer will ive the marimum effienfy when their fowwer loss is equal to the iron loss. From equaton (2) the value of outwut furrent I2 at whifh the transformer effienfy will e marimum is iven as If r is the frafton of full loa" KVA at whifh the effienfy of the transformer is marimum then, Cowwer losses = r2Pf (where Pf is the full loa" fowwer losses) Iron losses = Pi For marimum effienfy r2 Pf = Pi Therefore Thus, outwut KVA forreswon"in to marimum effienfy Puttin the value of r from the a ove equaton (3) in equaton (4) we will et, The a ove equaton (5) is the marimum effienfy fon"iton of the transformer.