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 80 % 90 % Less than 90% More than 90% 80 % 90 % Less than 90% More than 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) 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 5 % 6 % 4 % 0.4 % 5 % 6 % 4 % 0.4 % 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) A fixed step by step procedure for finding the solution of a problem on computer is called Algorithm Hardware Software Logic Algorithm Hardware Software Logic ANSWER DOWNLOAD EXAMIANS APP
DGVCL Exam Paper (11-12-2011) The main criterion for the design of a distributor is Radio interference Corona loss Voltage drop Temperature rise Radio interference Corona loss Voltage drop Temperature rise ANSWER DOWNLOAD EXAMIANS APP
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 0.8 lagging 0.6 lagging 0.5 leading 0.6 leading 0.8 lagging 0.6 lagging 0.5 leading 0.6 leading ANSWER DOWNLOAD EXAMIANS APP
DGVCL Exam Paper (11-12-2011) Which motor is used to start heavy loads? Shunt motor Differentially compounded motor Cumulatively compounded motor Series motor Shunt motor Differentially compounded motor Cumulatively compounded motor Series motor ANSWER EXPLANATION DOWNLOAD EXAMIANS APP Torque in d.c motor = k* φ * IaIn series motor φ α IaTα I²starting torque of dc series motor is high
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