Sparking at the commutator of a D.C. motor may result in____________?
A. damage to commutator segments
B. damage to commutator insulation
C. increased power consumption
D. all of the above
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
The total losses in a well designed D.C. generator of 10 kW will be nearly______________?
A. 100 W
B. 500 W
C. 1000 W
D. 1500 W
The condition for maximum efficiency for a D.C. generator is______________?
A. eddy current losses = stray losses
B. hysteresis losses = eddy current losses
C. copper losses = 0
D. variable losses = constant losses
The starting resistance of a D.C. motor is generally_______________?
A. low
B. around 500 Q
C. 1000 Q
D. infinitely large
What will happen if the back e.m.f. of a D.C. motor vanishes suddenly?
A. The motor will stop
B. The motor will continue to run
C. The armature may burn
D. The motor will run noisy
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