Electrical Machines The material used for commutator brushes is mostly cast iron. copper. mica. carbon. cast iron. copper. mica. carbon. ANSWER DOWNLOAD EXAMIANS APP
Electrical Machines A dc shunt motor runs at a no-load speed of 1140 rpm. At full load, armature reaction weakens the main flux by 5% whereas the armature circuit voltage drops by 10%. The motor full-load speed in rpm is 1200 1000 1080 1203 1200 1000 1080 1203 ANSWER DOWNLOAD EXAMIANS APP
Electrical Machines The demagnetising component of armature reaction in a DC generator results in sparking trouble. reduces generator emf. reduces inter poles flux density. increases armature speed. results in sparking trouble. reduces generator emf. reduces inter poles flux density. increases armature speed. 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. None of these coil resistance. armature emf. reactance voltage induced in the coil. None of these coil resistance. armature emf. ANSWER DOWNLOAD EXAMIANS APP
Electrical Machines A self-excited shunt generator fails to build up, because 1. the field circuit is open 2. The armature circuit is open 3. the residual magnetism is absent 4. The direction of rotation is wrong From these, the correct answer is 3 only 1, 3 1, 2 and 3 1, 2, 3 and 4 3 only 1, 3 1, 2 and 3 1, 2, 3 and 4 ANSWER DOWNLOAD EXAMIANS APP
Electrical Machines A 250 V DC generator in run at rated speed with no excitation. The open circuit voltage will be very small, say about 2 or 3 V. zero. about 100 V. 250 V. very small, say about 2 or 3 V. zero. about 100 V. 250 V. ANSWER DOWNLOAD EXAMIANS APP
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