DGVCL Exam Paper (11-12-2011) In the protection of transformers, harmonic restraint is used to guard against Magnetizing inrush current Unbalanced protection Lightning Switching over voltages Magnetizing inrush current Unbalanced protection Lightning Switching over voltages 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) An over excited synchronous motor draws current at Lagging power factor Depends on nature of load Unity power factor Leading power factor Lagging power factor Depends on nature of load Unity power factor Leading power factor ANSWER EXPLANATION DOWNLOAD EXAMIANS APP Over excitation : leading currentUnder excitation : lagging currentNormal excitation : current with unity PF (in phase current)
DGVCL Exam Paper (11-12-2011) An AC series circuit has R = 6 Ω, XL = 20 Ω and Xc = 12 Ω. The ciruit power factor will be 0.8 lagging 0.5 leading 0.6 lagging 0.6 leading 0.8 lagging 0.5 leading 0.6 lagging 0.6 leading 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? Conductor Resistor Voltage source Capacitor Conductor Resistor Voltage source Capacitor ANSWER DOWNLOAD EXAMIANS APP
DGVCL Exam Paper (11-12-2011) Due to skin effect Current flows through the half cross section of the conductor 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 Portion of the conductor near the surface carries more current and the core of the conductor carries less current Current flows through the half cross section of the conductor 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 Portion of the conductor near the surface carries more current and the core of the conductor carries less 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) Buchholz relay causes Tripping for both major and minor faults Alarm for both major and minor faults Tripping for major faults and alarm for minor faults Tripping for minor faults and alarm for major faults Tripping for both major and minor faults Alarm for both major and minor faults Tripping for major faults and alarm for minor faults Tripping for minor faults and alarm for major faults ANSWER DOWNLOAD EXAMIANS APP
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