DGVCL Exam Paper (11-12-2011) If the percentage reactance of the system upto the point of fault is 20% and the base kVA is 10,000 the short ciruit kVA is 20 MVA 60 MVA 50 MVA 10 MVA 20 MVA 60 MVA 50 MVA 10 MVA ANSWER EXPLANATION DOWNLOAD EXAMIANS APP Short circuit kVA = Base kVA/%X
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 0.4 % 5 % 6 % 4 % 0.4 % 5 % 6 % 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) In the protection of transformers, harmonic restraint is used to guard against Switching over voltages Lightning Magnetizing inrush current Unbalanced protection Switching over voltages Lightning Magnetizing inrush current Unbalanced protection 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 average value Peak value to average value Peak value to r.m.s value R.M.S. value to peak value R.M.S. value to average value Peak value to average value Peak value to r.m.s value R.M.S. value to peak value ANSWER DOWNLOAD EXAMIANS APP
DGVCL Exam Paper (11-12-2011) If a 5 A fuse is blown frequently in a house lighting circuit, it is required to Reduce the load Check the load Insert a fuse of higher current rating Insert a fuse of higher voltage rating Reduce the load Check the load Insert a fuse of higher current rating Insert a fuse of higher voltage rating ANSWER DOWNLOAD EXAMIANS APP
DGVCL Exam Paper (11-12-2011) The transient stability of a power system can be improved by Phase shifting transformer Single pole switching of circuit breakers Increasing the turbine valve opening Excitation control Phase shifting transformer Single pole switching of circuit breakers Increasing the turbine valve opening Excitation control ANSWER DOWNLOAD EXAMIANS APP
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