Electrical Machines The armature mmf in a dc machine is 1. stationary with respect to field poles 2. stationary with respect to armature 3. rotating with respect to field poles 4. rotating with respect to armature From these, the correct answer is 2, 3 2, 4 1, 3 1, 4 2, 3 2, 4 1, 3 1, 4 ANSWER DOWNLOAD EXAMIANS APP
Electrical Machines If the applied voltage of a certain transformer is increased by 50% and the frequency is reduced by 50%, the maximum flux density will (assuming that the magnetic circuit remains unsaturated) changes to 1.5 times the original value changes to 0.5 times the original value changes to three times the original value remain the same as the original changes to 1.5 times the original value changes to 0.5 times the original value changes to three times the original value remain the same as the original ANSWER DOWNLOAD EXAMIANS APP
Electrical Machines Field winding of a DC series motor is usually provided with thick wire in order to reduce eddy current to provide large flux. as it carries large load current. to reduce the insulation of materials. to provide large flux. in order to reduce eddy current to provide large flux. as it carries large load current. to reduce the insulation of materials. to provide large flux. 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 1, 2, 3 2, 3, 4, 5 2, 3 ,5 2, 3, 4 1, 2, 3 2, 3, 4, 5 2, 3 ,5 ANSWER DOWNLOAD EXAMIANS APP
Electrical Machines If the excitation of the synchronous generator fails, it acts as a/an induction generator. synchronous generator. synchronous motor. induction motor. induction generator. synchronous generator. synchronous motor. induction motor. ANSWER DOWNLOAD EXAMIANS APP
Electrical Machines R1 is the resistance of the primary winding of the transformer. The turn ratio in terms of primary to secondary is K. Then the equivalent resistance of the primary referred to secondary is R1 /K K×R1 K²R1 R1 /K² R1 /K K×R1 K²R1 R1 /K² ANSWER DOWNLOAD EXAMIANS APP
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