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The kVA rating of an ordinary 2-winding transformer is increased when connected as an autotransformer because:

The kVA rating of an ordinary 2-winding transformer is increased when connected as an autotransformer because: Correct Answer Energy is transferred both inductively and conductively

Autotransformer:

  • In an autotransformer, power is transferred through both conduction and induction processes.
  • EMF induced in the winding is proportional to the number of turns. Therefore, the secondary voltage can be varied by just varying a secondary number of turns.
  • Winding is common in both circuits, most of the energy is transferred by means of electrical conduction and a small part is transferred through induction.

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V2(I1 - I2) = Inductive transfer

V2I1 = Conductive transfer

Advantages of auto-transformer over a two-winding transformer:

  • More efficient for the same VA rating
  • Smaller in size
  • Require less copper in their construction
  • Cost is less compared to double wound transformers of the same VA rating
  • Core and copper losses are lower due to less resistance and leakage reactance giving a superior voltage regulation than the equivalent two winding transformer

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