Three single-phase two-winding transformers, each rated 3 kVA, 220/110 volts, 60 Hz, with a 0.10 per-unit leakage reactance, are connected as a three-phase extended Δ autotransformer bank, as shown in Figure 3.31(c). The low-voltage Δ winding has a 110 volt rating.
(a) Draw the positive-sequence phasor diagram and show that the highvoltage winding has a 479.5 volt rating.
(b) A three-phase load connected to the lowvoltage terminals absorbs 6 kW at 110 volts and at 0.8 power factor lagging.
Draw the per-unit impedance diagram and calculate the voltage and current at the high-voltage terminals. Assume positive-sequence operation.