Question

a) A three phase transformer rated at 30 MVA 10 kV(Δ)/1 kV(Y) is supplying a load...

a) A three phase transformer rated at 30 MVA 10 kV(Δ)/1 kV(Y) is supplying a load at the low voltage side. The load absorbs 5 MVA, 0.7 power factor lagging at line to line voltage 0.9 kV. The transformer has an equivalent reactance 0.05 Ω/phase. Assuming 10 MVA and 1 kV as base value, draw the per unit diagram for the system. Find the Line to Line voltage at the primary side of the transformer.

b) A three-phase synchronous generator rated 10 kV, 50 MVA has armature resistance 0.1 pu/phase and stator reactance 1.25 pu/phase. The machine operates at 10 kV infinite bus delivering power 20 MVA 0.9 pf. Determine the internal generated emf Ef and δ.

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