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 Less than 90% 90 % 80 % More than 90% Less than 90% 90 % 80 % 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) DC series motors are best suited for traction work because Its torque is proportional to the square of the armature current and speed is inversely proportional to torque Torque and speed are proportional to the square of the armature current Its torque is proportional to the square of the armature current and speed is directional proporational to torque Torque and speed are inversely proportional to the square of the armature current Its torque is proportional to the square of the armature current and speed is inversely proportional to torque Torque and speed are proportional to the square of the armature current Its torque is proportional to the square of the armature current and speed is directional proporational to torque Torque and speed are inversely proportional to the square of the armature current ANSWER EXPLANATION DOWNLOAD EXAMIANS APP Torque in d.c motor = k* φ * IaIn series motor φ α IaTα I²N α 1/φN α 1/T
DGVCL Exam Paper (11-12-2011) The purpose of providing a choke in a tube light is To limit the current to an appropriate value To improve the power factor To avoid radio interference To eliminate corona effect To limit the current to an appropriate value To improve the power factor To avoid radio interference To eliminate corona effect ANSWER DOWNLOAD EXAMIANS APP
DGVCL Exam Paper (11-12-2011) The bus bar zone faults are generally Three phase short ciruits Double line to ground faults Single line to ground faults Phase to phase faults Three phase short ciruits Double line to ground faults Single line to ground faults Phase to phase faults ANSWER DOWNLOAD EXAMIANS APP
DGVCL Exam Paper (11-12-2011) Which of the following correctly represents the sequence of operations of isolator, circiut breaker and earthing switch while opening a circuit? Open circuit breaker-open isolator-close earthing switch Open isolator close circuit breaker-open earthing switch Close earthing switch - open ciruit- breaker-open islotor Close circuit breaker-close isolator - open earthing switch Open circuit breaker-open isolator-close earthing switch Open isolator close circuit breaker-open earthing switch Close earthing switch - open ciruit- breaker-open islotor Close circuit breaker-close isolator - open earthing switch ANSWER DOWNLOAD EXAMIANS APP
DGVCL Exam Paper (11-12-2011) Ybus used in power flow studies and Zbus used in short circuit studies Are transpose of each other Are inverse of each other Are the same Have no inter relation Are transpose of each other Are inverse of each other Are the same Have no inter relation ANSWER DOWNLOAD EXAMIANS APP
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