Electrical Machines The residual magnetism of a self-excited dc generator is lost. To build up its emf again field winding must be excited by low voltage dc supply the field winding connection must be reversed the field winding must be replaced the armature connection must be reversed field winding must be excited by low voltage dc supply the field winding connection must be reversed the field winding must be replaced the armature connection must be reversed ANSWER DOWNLOAD EXAMIANS APP
Electrical Machines To avoid formation of grooves in the commutator the brushes of opposite polarity should track each other. None of these brush position has no effect on the commutator grooving. the brushes of same polarity should track each other. the brushes of opposite polarity should track each other. None of these brush position has no effect on the commutator grooving. the brushes of same polarity should track each other. ANSWER DOWNLOAD EXAMIANS APP
Electrical Machines For satisfactory performance of 3-phase 480V, 60 Hz induction motor, the supply voltage at 50 Hz should be equal to 480 V. 350 V. 420 V. 400 V. 480 V. 350 V. 420 V. 400 V. ANSWER DOWNLOAD EXAMIANS APP
Electrical Machines If the armature electric current is increased to double its previous value, and the time of commutation is halved, how will the reactance voltage vary? It will be doubled. It will remain the same. It will becomes four times. It will be halved. It will be doubled. It will remain the same. It will becomes four times. It will be halved. 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%. 82.5% 72.5% 78.5% 67.5% 82.5% 72.5% 78.5% 67.5% ANSWER DOWNLOAD EXAMIANS APP
Electrical Machines In speed control of DC Series motor, speed lower than the rated speed can be obtained by Connecting an additional resistance in the field circuit. Connecting an additional resistance in stator circuit. Any of the above. Connecting an additional resistance in the armature circuit. Connecting an additional resistance in the field circuit. Connecting an additional resistance in stator circuit. Any of the above. Connecting an additional resistance in the armature circuit. ANSWER DOWNLOAD EXAMIANS APP
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