A 230-kVA, 2300/230-V, 60-Hz, step-down, two-winding transformer has the following parameters RH = 1.2 Ohm, XH = 3 Ohm, RL = 12 mOhm, XL = 30 mOhm, RcH = 2 kOhm, XmH = 1.8 kOhm. A) If the transformer operates at half load at its rated terminal voltage with a unity power factor, what is its efficiency? B) If the transformer is operating at 80% of its load, at secondary terminal voltage of 216 V and 0.866 pf lagging, what is its efficiency?

When the transformer is loaded in a balanced fashion up to its nominal rating (10 MVA), calculate the high side line-to-line phasor voltages (ab, bc, ca). and low side phasor voltages both line-to-line and line-to-neutral (ab, bc, ca, a, b,c). as a reference for calculations the low side A line to neutral voltage is 7620V at an angle of 0 degrees when the transformer is at rated power.  The transformer has the following characteristics: V: 138kV delta high side/ 13.2 kV wye low side 9% impedance X/R ratio of 20

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