DGVCL Exam Paper (11-12-2011) In the protection of transformers, harmonic restraint is used to guard against Unbalanced protection Magnetizing inrush current Switching over voltages Lightning Unbalanced protection Magnetizing inrush current Switching over voltages Lightning ANSWER EXPLANATION DOWNLOAD EXAMIANS APP Initial inrush of magnetizing currents have high component of even and odd harmonics.2nd - 63%3rd -26.8%4th- 5.1%5th- 4.1%6th- 3.77th-2.4
DGVCL Exam Paper (11-12-2011) The form factor in AC means the ration of R.M.S. value to peak value Peak value to average value Peak value to r.m.s value R.M.S. value to average value R.M.S. value to peak value Peak value to average value Peak value to r.m.s value R.M.S. value to average value 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 % 4 % 5 % 0.4 % 6 % 4 % 5 % 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) Hysteresis in an instrument means The inaccuracy due to change in temperature The repeatability of the instrument The reliability of the instrument The change in the same reading when the input is first increased and then decreased The inaccuracy due to change in temperature The repeatability of the instrument The reliability of the instrument The change in the same reading when the input is first increased and then decreased ANSWER DOWNLOAD EXAMIANS APP
DGVCL Exam Paper (11-12-2011) The advantage of slipring induction motor over the squirrel cage induction motor is It has a higher efficiency It is suitable for higher speeds It can be started with the help of rotor resistances It's power factor is higher It has a higher efficiency It is suitable for higher speeds It can be started with the help of rotor resistances It's power factor is higher ANSWER EXPLANATION DOWNLOAD EXAMIANS APP slip ring motor have high starting torque compare to squirrel cage motor and have good speed controlalso have high over loading capacity, smooth acceleration under heavy loads.
DGVCL Exam Paper (11-12-2011) In carrier current protection, the purpose of the wave trap is for Trapping power frequency waves Tripping fault current All of these Trapping high frequency waves entering into generator/transformer unit. Trapping power frequency waves Tripping fault current All of these Trapping high frequency waves entering into generator/transformer unit. ANSWER DOWNLOAD EXAMIANS APP
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