DGVCL Exam Paper (11-12-2011) Permittivity is expressed in terms of farad/sq. m. N/m Farad/m Weber /m farad/sq. m. N/m Farad/m Weber /m ANSWER DOWNLOAD EXAMIANS APP
DGVCL Exam Paper (11-12-2011) The transient stability of a power system can be improved by Single pole switching of circuit breakers Excitation control Phase shifting transformer Increasing the turbine valve opening Single pole switching of circuit breakers Excitation control Phase shifting transformer Increasing the turbine valve opening 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 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) The form factor in AC means the ration of 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 R.M.S. value to average value ANSWER DOWNLOAD EXAMIANS APP
DGVCL Exam Paper (11-12-2011) Due to skin effect Current flows through the half cross section of the conductor Portion of the conductor near the surface carries more current and the core of the conductor carries less current Uniform current flows through the conductor Portion of the conductor near the surface carries less current and the core of the conductor carries more current Current flows through the half cross section of the conductor Portion of the conductor near the surface carries more current and the core of the conductor carries less current Uniform current flows through the conductor Portion of the conductor near the surface carries less current and the core of the conductor carries more current ANSWER EXPLANATION DOWNLOAD EXAMIANS APP Skin Effect:tendency of the current to crowd near the conductor surface.Skin effect is proportional to frequency, conductor diameter and permiability. Skin effect increases effective resistance of conductor.In DC, no skin effect.
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 50 MVA 60 MVA 10 MVA 20 MVA 50 MVA 60 MVA 10 MVA ANSWER EXPLANATION DOWNLOAD EXAMIANS APP Short circuit kVA = Base kVA/%X
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