A 13,800/480 V three-phase Wye-Delta-connected transformer bank consists of three identical 100-kVA 7967/480-V transformers. It is supplied with power directly from a large constant-voltage bus. In the short-circuit test, the recorded values on the high-voltage side for one of these transformers are
Vsc = 560 V
Isc = 12.6 A
Psc = 3300 W
If this bank delivers a rated load at 0.85 PF lagging and rated voltage, what is the line-to-line voltage on the primary of the transformer bank?
What is the voltage regulation under these conditions?
Note: In this problem, the core resistance and mutual inductance shall be ignored. The "13,800/480 V" means line-line voltage at primary is 13.8 kV and the line-line voltage and secondary is 480 V. Both are RMS values.