Question

In: Electrical Engineering

A three phase transformer of 400kVA, 10kV/400V, Dy11 is connected to its nominal load with cosφ...

A three phase transformer of 400kVA, 10kV/400V, Dy11 is connected to its nominal load with cosφ = 1.

a) Calculate the nominal primary and secondary line current.
b) Calculate the corresponding currents in the primary and secondary winding.

At an open circuit test, the primary line current is 0,52A with cosφ = 0,05 at nominal line voltage.
The short circuit test (at nominal current) shows 214V primary line voltage and P=1,333kW per phase.

c) Calculate the total iron losses and total copper losses of this transformer.

d) Calculate the efficiency η of this transformer.

Now the transformer will be loaded with 210kW with cosφ = 0,83 (lagging).

e) Give both the iron losses and the copper losses as a percentage of what they are nominally.

Please show process and computations with comments.

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