A. severe sparking
B. rough commutator surface
C. imperfect contact
D. any of the above
Related Mcqs:
- Two generators are running in parallel. One of the generators may run as motor for which of the following reasons ?
A. The direction of that generator is reversed
B. The speed of that generator is increased
C. The field of that generator is weakened
D. That generator takes large share of loads - The rapid wear of brushes takes place due to____________?
A. abrasion from dust
B. excessive spring pressure
C. rough commutator bars
D. high mica insulation between com-mutation bars
E. all of the above factors - The voltage drop for which of the following types of brush can be expected to be least ?
A. Graphite brushes
B. Carbon brushes
C. Metal graphite brushes
D. None of the above - Following energized winding of a D.C. machine should not be opened as it would produce high inductive voltage which may be dangerous to personnel and may cause its own insulation failure.
A. Series field
B. Compensating field
C. Inter pole field
D. Shunt field - Which of the following statement about D.C. generators is false ?
A. Compensating winding in a D.C. machine helps in commutation
B. In a D. C. generator interpoles winding is connected in series with the armature winding
C. Back pitch and front pitch are both odd and approximately equal to the pole pitch
D. Equilizing bus bars are used with parallel running of D.C. shunt gen¬erators - Two generators A and B have 6-poles each. Generator A has wave wound armature while generator B has lap wound armature. The ratio of the induced e.m.f. is generator A and B will be_______________?
A. 2 : 3
B. 3 : 1
C. 3 : 2
D. 1 : 3 - Which of the following D.C. generators will be in a position to build up without any residual magnetism in the poles?
A. Series generator
B. Shunt generator
C. Compound generator
D. None of the above - In D.C. generators on no-load, the air gap flux distribution in space is______________?
A. sinusoidal
B. triangular
C. pulsating
D. flat topped - Which of the following generators will be preferred if they are required to be run in parallel?
A. Shunt generators
B. Series generators
C. Compound generators
D. None of the above - The main factor which leads to unstable parallel operation of flat and over compounded generators is_____________?
A. their rising voltage characteristics
B. unequal number of turns in their series field windings
C. unequal speed regulation of their primemovers
D. unequal series field resistances
