TRANSFORMER QUESTION!!! PLS HELP

I have a problem that has caused me so many trouble!! I hope someone can help me on this

the question is I got two identical 50kVA 400/2000V single phase transfers operating in parallel that is supplying a computer of 40kVA at 2000V and 0.80 PF leading.
I did a short cct test measured on the primary side of the transformer and Vprimary =31.622V and Pprimary=1250W
I want to find the primary voltage of the transformers neglecting no load losses and magnetizing effects and also the efficiency of the transformer bank operating for this load

thx.. I tried to look up books to solve this but I cannot..it is so hard!!! Please help me

 

there was a typo, I meant to say TRANSFORMER when I said transfer in the above posting

 

[230842]

I'll try to help you. I supose short circuit test correspond to only one transformer. From that, we can get s.c. impedance (referred to primary): Zscp = Uscp/ Ip = 31'622 V/125 A = 0.253 ohms. Resistance of that impedance can be got from power: R = P/I^2 = 1250 / 125^2 = 0.08 ohms. Reactance is then: X = sqrt(Zcc^2 - R^2) = sqrt(0.253^2 - 0.08^2) = 0.24 ohms.
Now primary voltage can be got, assuming each transformer processes the half of secondary load, adding to secondary voltage, referred to primary, the internal voltage drop due to primary current flowing through s.c. impedance. Using phasorial magnitudes and complex impedances:
Secondary voltage (ref. to primary): 400 V (phasor: 400 / 0º V)
Current (primary): Ip = S/2U = 40,000/2x400 = 50 A (phasor: 50 / -36.87º A)
S.c. complex impedance (primary): Zscp = 0.08 + j0.24 ohms = 0.253 / 71.56º ohms.
Internal voltage drop phasor (primary): dVi = 50 / -36.87ºx 0.253 / 71.56º = 12.65 / 34.7º V
Primary voltage phasor: 400 / 0º+ 12.65 / 34.7º = 410.5 / 1º V.


Any additional doubt?
Julian