Electrical Machines
Which of the following factors improve commutation in a dc machine ? 1. High contact resistance of brushes 2. High inductance of the coils undergoing commutation 3. Shifting of brushes in the direction of rotation for a generator and in the opposite direction For a motor 4. Narrow width for the commutation bars Select the correct answer using the codes given below : Codes :

 1, 2 and 4
 1 and 3
 2, 3 and 4
 1, 2, and 3

ANSWER DOWNLOAD EXAMIANS APP

Electrical Machines
In a loaded DC generator, if the brushes are given a shift from the interpolar axis in the direction of rotation, then the commutation will

 improve with rise in terminal voltage.
 improve with fall of terminal voltage.
 deteriorate with rise in terminal voltage.
 deteriorate with fall of terminal voltage.

ANSWER DOWNLOAD EXAMIANS APP