MGVCL Exam Paper (30-07-2021 Shift 2)
A 1000 kVA ONAN cooled transformer has a load of 500 kVA throughout the day except for a period of 4 hours. What is the permissible overload for a duration of four hours. Assume the permissible load kVA as a fraction of rated kVA is 1.24.
Where, Pmp is maximum power in watt Vmp maximum voltage at maximum power in volt Imp is maximum current at maximum power in ampere Voc open circuit voltage in volt Isc is short circuit current in ampere
Fill Factor = Pmp/(Vosc*Isc) = (Vmp*Imp)/(Voc*Isc) = (2.65*0.5)/(0.7*3) = 0.63
Equivalent resistance of the circuit, Req = (12||18) + 8 Req = 7.2 + 8 Req = 15.2 ohm Source current = current through 8 ohm resistor, I = Vr/R8 I = 20/8 I = 2.5 A Supply votage V = I*Req V = 2.5*15.2 V = 38 V
EXAMIANS