Three single-phase, 10-kVA, 2400/120-V, 60-Hz transformers are connected to a three-phase, 4160/208-V transformer bank. The equivalent impedance of each single-phase transformer referred to the primary side is 10 + j25 Ω. The transformer bank delivers 27 kW at 208 V and 0.9 power factor leading.

a. Draw the three-phase schematic diagram showing the transformer connection. Draw a per-phase equivalent circuit.
b. Determine the primary current and power factor.
c. Determine the primary voltage.
d. Determine the voltage regulation.