Electrical Machines The residual magnetism of a self-excited dc generator is lost. To build up its emf again the field winding connection must be reversed the armature connection must be reversed field winding must be excited by low voltage dc supply the field winding must be replaced the field winding connection must be reversed the armature connection must be reversed field winding must be excited by low voltage dc supply the field winding must be replaced ANSWER DOWNLOAD EXAMIANS APP
Electrical Machines A 4-pole dc generator runs at 1500 rpm. The frequencyof current in the armature winding is 100 Hz 50 Hz 25 Hz 0 Hz 100 Hz 50 Hz 25 Hz 0 Hz ANSWER DOWNLOAD EXAMIANS APP
Electrical Machines The current drawn by the a 230 V DC motor of armature resistance 0.5 Ω and back emf 200 V is 60 600 40 660 60 600 40 660 ANSWER DOWNLOAD EXAMIANS APP
Electrical Machines The fall in speed of the DC generator due to increase in load can be corrected by increasing the input to the prime mover. reducing the load voltage. increasing the excitation. cooling the armature. increasing the input to the prime mover. reducing the load voltage. increasing the excitation. cooling the armature. ANSWER DOWNLOAD EXAMIANS APP
Electrical Machines What is the necessity of copper brushes in a dc motors? To increase the flux cutting by the rotor. To absorb the mechanical shocks produced during running condition. None of these. To convert alternating supply current to direct current. To increase the flux cutting by the rotor. To absorb the mechanical shocks produced during running condition. None of these. To convert alternating supply current to direct current. ANSWER DOWNLOAD EXAMIANS APP
Electrical Machines If the temperature of armature resistance is increased, the speed of a series motor would not change. None of above. increase. decrease. not change. None of above. increase. decrease. ANSWER DOWNLOAD EXAMIANS APP
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