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
Related Mcqs:
- The speed of a D.C. shunt motor more than its full-load speed can be obtained by_____________?
A. decreasing the field current
B. increasing the field current
C. decreasing the armature current
D. increasing the armature current - Speed control by Ward Leonard method gives uniform speed variation_____________?
A. in one direction
B. in both directions
C. below normal speed only
D. above normal speed only - The speed of a motor falls from 1100 r.p.m. at no-load to 1050 r.p.m. at rated load. The speed regulation of the motor is______________?
A. 2.36%
B. 4.76%
C. 6.77%
D. 8.84% - The speed of a D.C. shunt motor is required to be more than full load speed. This is possible by______________?
A. reducing the field current
B. decreasing the armature current
C. increasing the armature current
D. increasing the excitation current
E. none of the above methods - In case of D.C. shunt motors the speed is dependent on back e.m.f. only because____________?
A. back e.m.f. is equal to armature drop
B. armature drop is negligible
C. flux is proportional to armature current
D. flux is practically constant in D:C. shunt motors - To get the speed of D.C, motor below the normal without wastage of electrical energy is used?
A. Ward Leonard control
B. rheostatic control
C. any of the above method
D. none of the above method - For the same H.P. rating and full load speed, following motor has poor starting torque_____________?
A. shunt
B. series
C. differentially compounded
D. cumulativelyc’ompounded - As -the load is increased the speed of D.C. shunt motor will____________?
A. reduce slightly
B. increase slightly
C. increase proportionately
D. remains unchanged - The speed of a D.C. shunt motor can be increased by_______________?
A. increasing the resistance in armature circuit
B. increasing the resistance in field circuit
C. reducing the resistance in the field circuit
D. reducing the resistance in the armature circuit - If the load on a DC shunt motor is increases, its speed is slightly reduced due to______________?
A. increase in armature current
B. increase in flux
C. decrease in reactance
D. decrease in back emf
