DC Motors Objective Questions and Answers

351. In a shunt generator the voltage build up is generally restricted by

352. I1 a D.C. generator fails to build up the probable cause could not be

A. imperfect brush contact

B. field resistance less than the critical resistance

C. no residual magnetism in the generator

D. fault shunt connections tending to reduce the residual magnetism

Discussion

353. Flashing the field of D.C. generator means

A. neutralising residual magnetism

B. creating residual magnetism by a D.C. source

C. making the magnetic losses of forces parallel

D. increasing flux density by adding extra turns of windings on poles

Discussion

354. The e.m.f. induced in the armature of a shunt generator is 600 V. The armature resistance is 0.1 ohm. If the armature current is 200 A, the terminal voltage will be

355. 1n a D.C. generator the critical resistance refers to the resistance of

356. To achieve sparkless commutation brushes of a D.C. generator are rocked ahead so as to bring them

A. just ahead of magnetic neutral axis

B. along magnetic neutral axis

C. just behind the magnetic neutral axis

D. just ahead of geometric neutral axis

Discussion

357. Armature coil is short-circuited by brushes when it lies

A. along neutral axis

B. along field axis

C. in any of the above positions

D. in none of the above positions

Discussion

Electrical Engineering Objective Questions { DC Motors }