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% 80 % Less than 90% 90 % More than 90% 80 % Less than 90% 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) In which of the following motors, the stator and rotor magnetic fields rotate at the same speed? Synchronous motor Universal motor Reluctance motor Induction motor Synchronous motor Universal motor Reluctance motor Induction motor ANSWER EXPLANATION DOWNLOAD EXAMIANS APP In all machine stator and rotor magnetic field rotates (stationary with respect to each other) at synchronous speed with respect to stationary observer.
DGVCL Exam Paper (11-12-2011) The insulation coordination for UHV lines (above 500 kV) is done based on Lightning surges Lightning and switching surges Voltage level of the line Switching surges Lightning surges Lightning and switching surges Voltage level of the line Switching surges ANSWER DOWNLOAD EXAMIANS APP
DGVCL Exam Paper (11-12-2011) Hysteresis in an instrument means The repeatability of the instrument The change in the same reading when the input is first increased and then decreased The reliability of the instrument The inaccuracy due to change in temperature The repeatability of the instrument The change in the same reading when the input is first increased and then decreased The reliability of the instrument The inaccuracy due to change in temperature ANSWER DOWNLOAD EXAMIANS APP
DGVCL Exam Paper (11-12-2011) Reactance relay is used to protect against Earth faults only Over voltage faults Phase faults only Both phase and earth faults Earth faults only Over voltage faults Phase faults only Both phase and earth faults ANSWER DOWNLOAD EXAMIANS APP
DGVCL Exam Paper (11-12-2011) At time t= 0+ , with zero initial condition, which of the following acts as a short circuit? Capacitor Conductor Voltage source Resistor Capacitor Conductor Voltage source Resistor ANSWER DOWNLOAD EXAMIANS APP
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