DGVCL Exam Paper (11-12-2011) Due to skin effect Uniform current flows through the conductor Current flows through the half cross section of 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 Uniform current flows through the conductor Current flows through the half cross section of 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) DC series motors are best suited for traction work because Torque and speed are proportional to the square of the armature current Its torque is proportional to the square of the armature current and speed is inversely proportional to torque Its torque is proportional to the square of the armature current and speed is directional proporational to torque Torque and speed are inversely proportional to the square of the armature current Torque and speed are proportional to the square of the armature current Its torque is proportional to the square of the armature current and speed is inversely proportional to torque Its torque is proportional to the square of the armature current and speed is directional proporational to torque Torque and speed are inversely proportional to the square of the armature current ANSWER EXPLANATION DOWNLOAD EXAMIANS APP Torque in d.c motor = k* φ * IaIn series motor φ α IaTα I²N α 1/φN α 1/T
DGVCL Exam Paper (11-12-2011) The insulation coordination for UHV lines (above 500 kV) is done based on Lightning surges Switching surges Lightning and switching surges Voltage level of the line Lightning surges Switching surges Lightning and switching surges Voltage level of the line ANSWER DOWNLOAD EXAMIANS APP
DGVCL Exam Paper (11-12-2011) The corona effect can be minimized by increasing Spacing between the conductors Both spacing between the conductors and diameter of the conductor Diameter of the conductor The length of the conductor Spacing between the conductors Both spacing between the conductors and diameter of the conductor Diameter of the conductor The length of the conductor ANSWER EXPLANATION DOWNLOAD EXAMIANS APP Corona can be reduced by using large size of conductor, bundle conductor and hollow conductor.
DGVCL Exam Paper (11-12-2011) The circuit breaker generally used in railway traction is Minimum Oil CB Air break CB Vacuum CB Bulk Oil CB Minimum Oil CB Air break CB Vacuum CB Bulk Oil CB ANSWER DOWNLOAD EXAMIANS APP
DGVCL Exam Paper (11-12-2011) If the excitation of a synchronous generator fails, it acts as a Synchronous motor Induction motor Synchronous generator Induction generator Synchronous motor Induction motor Synchronous generator Induction generator ANSWER EXPLANATION DOWNLOAD EXAMIANS APP if excitation of synchronous generator fails, operate as induction motor
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