A 1 MVA three-phase 6,600/400V delta/star connected transformer has the following parameters per phase.
HV side: R1 = 1.307 ohms X1 = 5.228 ohms
LV side: R2 = 0.0016 ohms X2 = 0.0064 ohms
(a) Calculate the per unit impedance of the transformer using base values of 1 MVA and 400 V. (and .)
(b) The transformer delivers 700 kVA at 0.85 power factor lagging to a three-phase balanced load at a line voltage of 400V.
Calculate the line voltage at the secondary terminals of the transformer if the load is disconnected from the transformer. Assume that the input voltage to the transformer remains unchanged. Neglect core loss and magnetizing current.