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 2, 3 ,5 1, 2, 3 2, 3, 4, 5 2, 3, 4 2, 3 ,5 1, 2, 3 2, 3, 4, 5 ANSWER DOWNLOAD EXAMIANS APP
Electrical Machines φA 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 speed when running as a motor taking 40 A at 250 V. Armature reaction weakens the field by 4%. 970 RPM 940 RPM 960 RPM 920 RPM 970 RPM 940 RPM 960 RPM 920 RPM ANSWER DOWNLOAD EXAMIANS APP
Electrical Machines Which of the following motor is more expensive for same KW output rating ? AC single phase motor. Induction motor. DC Shunt Motor Synchronous motor. AC single phase motor. Induction motor. DC Shunt Motor Synchronous motor. ANSWER DOWNLOAD EXAMIANS APP
Electrical Machines A dc shunt generator, when commissioned after a major repair of the field system, failed to build Up voltage. It was because field resistance was higher than critical resistance there was a break in the armature circuit field system lost residual magnetism field winding was wrongly connected field resistance was higher than critical resistance there was a break in the armature circuit field system lost residual magnetism field winding was wrongly connected ANSWER DOWNLOAD EXAMIANS APP
Electrical Machines Current in a coil undergoing commutation is not able to get reversed completely by the end of commutation period. It is due to reactance voltage induced in the coil. armature emf. coil resistance. None of these reactance voltage induced in the coil. armature emf. coil resistance. None of these ANSWER DOWNLOAD EXAMIANS APP
Electrical Machines The use of double squirrel cage winding on the rotor provides reduced starting torque. a large starting torque. higher efficiency. low noise. reduced starting torque. a large starting torque. higher efficiency. low noise. ANSWER DOWNLOAD EXAMIANS APP
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