DGVCL Exam Paper (11-12-2011) The efficiency of a transformer at full load, 0.8 p.f. lag is 90%. Its efficiency at full load, 0.8 p.f. lead will be More than 90% Less than 90% 80 % 90 % More than 90% Less than 90% 80 % 90 % ANSWER EXPLANATION DOWNLOAD EXAMIANS APP Efficiency= output power/input powerefficiency = (v*i*cosφ)/((v*i*cosφ)+(x² Pc)+(Pi)) x=fractional part of full load
DGVCL Exam Paper (11-12-2011) An AC series circuit has R = 6 Ω, XL = 20 Ω and Xc = 12 Ω. The ciruit power factor will be 0.6 lagging 0.8 lagging 0.5 leading 0.6 leading 0.6 lagging 0.8 lagging 0.5 leading 0.6 leading ANSWER DOWNLOAD EXAMIANS APP
DGVCL Exam Paper (11-12-2011) A 3 phase, 6 pole induction motor operates on 440 V, 50 Hz, supply. If the actual speed of the motor is 960 rpm the slip will be 6 % 0.4 % 5 % 4 % 6 % 0.4 % 5 % 4 % ANSWER EXPLANATION DOWNLOAD EXAMIANS APP Ns = 120f/PSlip=(Ns-Nr)/NsNs = 1000 and Nr = 960 from equation of slip, S = (1000-960)/1000S = 0.04 or 4%
DGVCL Exam Paper (11-12-2011) Fot fast load flow calculations, the best method is De-coupled method Newton-Raphson Gauss-Siedal Approximate method De-coupled method Newton-Raphson Gauss-Siedal Approximate method ANSWER DOWNLOAD EXAMIANS APP
DGVCL Exam Paper (11-12-2011) A fuse wire should have Low specific resistance and high melting point Low specific resistance and low melting point High specific resistance and low melting point High specific resistance and high melting point Low specific resistance and high melting point Low specific resistance and low melting point High specific resistance and low melting point High specific resistance and high melting point ANSWER DOWNLOAD EXAMIANS APP
DGVCL Exam Paper (11-12-2011) The bus bar zone faults are generally Double line to ground faults Phase to phase faults Single line to ground faults Three phase short ciruits Double line to ground faults Phase to phase faults Single line to ground faults Three phase short ciruits ANSWER DOWNLOAD EXAMIANS APP
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