Where D.C. motor of H.P. 12 or more requires frequent starting, stopping, reversing and speed control______________?
(A) drum type controller is used
(B) three point starter is used
(C) four point starter is used
(D) all above can be used
When the armature of a D.C. motor rotates, e.m.f. induced is___________?
(A) self-induced e.m.f.
(B) mutually induced e.m.f.
(C) back e.m.f
(D) none of the above
In variable speed motor___________?
(A) a stronger commutating field is needed at low speed than at high speed
(B) a weaker commutating field is needed at low speed than at high speed
(C) same commutating field is needed at low speed than at high speed
(D) none of the above is correct
Which method of braking is generally used in elevators ?
(A) Plugging
(B) Regenerative braking
(C) Rheostatic braking
(D) None of the above
For which types of D.C. motor, dynamic braking is generally used ?
(A) Shunt motors
(B) Series motors
(C) Compound motors
(D) All of the above
Hopkinson’s test on D.C. machines is conducted at_______________?
(A) no-load
(B) part load
(C) full-load
(D) overload
Which of the following method is used for the speed control of DC shunt motor?
(A) voltage control method
(B) flux control method
(C) rheostat control method
(D) all of the above
If the field winding resistance of a DC shunt motor is increases, its speed will____________?
(A) decreases
(B) increases
(C) remains same
(D) none of the above
With the increase in temperature, the speed of DC series motor______________?
(A) decreases
(B) increases
(C) remain same
(D) none of the above
With the increase in temperature, the speed of DC shunt motor____________?
(A) decreases.
(B) increases
(C) remain same
(D) none of the above