Electrical Machines In DC generators, the cause of rapid brush wear may be rough commutator surface. severe sparking. imperfect contact. any of above. rough commutator surface. severe sparking. imperfect contact. any of above. ANSWER DOWNLOAD EXAMIANS APP
Electrical Machines A DC shunt machine generates 250 V on open circuit at 1000 RPM. Armature resistance is 0.5 Ω, field resistance 250 Ω. When running as a motor takes 4 A at 250 V. Calculate the efficiency when running as a motor taking 40 A at 250 V. Armature reaction weakens the field by 4%. 72.5% 67.5% 82.5% 78.5% 72.5% 67.5% 82.5% 78.5% ANSWER DOWNLOAD EXAMIANS APP
Electrical Machines Oil is provided in an oil filled transformer for both cooling and insulation. lubrication. cooling. insulating. both cooling and insulation. lubrication. cooling. insulating. ANSWER DOWNLOAD EXAMIANS APP
Electrical Machines A commutator in DC machines can 1. provide half-wave rectification 2. Provide full-wave rectification 3. convert ac to dc 4. Convert dc to ac 5. provide controlled full-wave rectification From these, the correct answer is 2, 3, 4, 5 2, 3, 4 2, 3 ,5 1, 2, 3 2, 3, 4, 5 2, 3, 4 2, 3 ,5 1, 2, 3 ANSWER DOWNLOAD EXAMIANS APP
Electrical Machines The introduction of interpoles in between the main poles improves the performance of a dc machine, because the flux waveform is improved with reduction in harmonics a counter-emf is induced in the coil undergoing commutation the inequality of air-gap flux on the top and bottom halves of the armature is removed the interpoles produce additional flux to augment the developed torque the flux waveform is improved with reduction in harmonics a counter-emf is induced in the coil undergoing commutation the inequality of air-gap flux on the top and bottom halves of the armature is removed the interpoles produce additional flux to augment the developed torque ANSWER DOWNLOAD EXAMIANS APP
Electrical Machines In which of the following DC Motor the ratio of starting torque to full load torque is minimum? Differential compound motor. Shunt motor. Series motor. Cumulative compound motor. Differential compound motor. Shunt motor. Series motor. Cumulative compound motor. ANSWER DOWNLOAD EXAMIANS APP
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