A. to improve cooling
B. to reduce copper losses
C. to increase the generated e.m.f.
D. to reduce the sparking
Related Mcqs:
- In case of conductively compensated D.C. series motors, the compensating winding is provided______________?
A. as separately wound unit
B. in parallel with armature winding
C. in series with armature winding
D. in parallel with field winding - If the field winding resistance of a DC shunt motor is increases, its speed will____________?
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 - In a DC motor the inter-pole winding is connected in________________?
A. series with field winding
B. series speed armature winding
C. parallel big field winding
D. parallel with armature winding - In D.C. machines the residual magnetism is of the order of_________________?
A. 2 to 3 per cent
B. 10 to 15 per cent
C. 20 to 25 per cent
D. 50 to 75 per cent - The purpose of retardation test on D.C. shunt machines is to find out____________?
A. stray losses
B. eddy current losses
C. field copper losses
D. windage losses - Hopkinson’s test on D.C. machines is conducted at_______________?
A. no-load
B. part load
C. full-load
D. overload - According to Fleming’s left-hand rule, when the forefinger points in the direction of the field or flux, the middle finger will point in the direction of_________________?
A. current in the conductor aovtaat of conductor
C. resultant force on conductor
D. none of the above - If a D.C. shunt motor is working at no load and if shunt field circuit suddenly opens__________?
A. nothing will happen to the motor
B. this will make armature to take heavy current, possibly burning it
C. this will result in excessive speed, possibly destroying armature due to excessive centrifugal stresses D. motor will run at very slow speed - Which motor has the poorest speed control?
A. Differentially compounded motor
B. Cumulatively compounded motor
C. Shunt motor
D. Series motor - Which of the following tests will be suitable for testing two similar D.C. series motors of large capacity ?
A. Swinburne’s test
B. Hopkinson’s test
C. Field test
D. Brake test
