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 % 0.4 % 4 % 6 % 5 % 0.4 % 4 % 6 % 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) The form factor in AC means the ration of 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 R.M.S. value to peak value Peak value to average value ANSWER DOWNLOAD EXAMIANS APP
DGVCL Exam Paper (11-12-2011) In a series RLC circuit at resonance Current is maximum and power factor is 0.5 Current is minimum and power factor is unity Current is maximum and power factor is unity Current is minimum and power factor is 0.5 Current is maximum and power factor is 0.5 Current is minimum and power factor is unity Current is maximum and power factor is unity Current is minimum and power factor is 0.5 ANSWER DOWNLOAD EXAMIANS APP
DGVCL Exam Paper (11-12-2011) In the protection of transformers, harmonic restraint is used to guard against Lightning Unbalanced protection Switching over voltages Magnetizing inrush current Lightning Unbalanced protection Switching over voltages Magnetizing inrush current 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) 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 50 MVA 10 MVA 20 MVA 60 MVA 50 MVA 10 MVA 20 MVA 60 MVA ANSWER EXPLANATION DOWNLOAD EXAMIANS APP Short circuit kVA = Base kVA/%X
DGVCL Exam Paper (11-12-2011) Which motor is used to start heavy loads? Shunt motor Cumulatively compounded motor Series motor Differentially compounded motor Shunt motor Cumulatively compounded motor Series motor Differentially compounded 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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