Q.466 A D.O.L starter is employed for starting electric motor of rating upto
A. 1HP
B. 3.75 HP
C. more than 10 HP
D. Upto 10 HP
Ans.: B
Q.467 A single phasw transformer has specifications 250 KVa, 11000V/415 V, 50 Hz. Which are the approx. value of primary and secondary currents?
A. Ip = 22.7 A, Is = 602 A
B. Ip = 602 A, Is = 22.7A
C. Ip = 301 A, Is = 22.7 A
D. Ip = 11.4 A, Is = 301 A
Ans.: A
Q.468 The core flux of a practical transformer with a resistance load
A. is strictly constant with load changes
B. increases linearly with load
C. increases as the square root of the load
D. decreases with increase in load
Ans.: A
Q.469 For better result in transformer
A. Both OC and SC test are conducted on LV side
B. Both OC and SC test are conducted on HV side
C. OC test on LV side and SC test on HV side
D. OC test on HV side and SC test on LV side
Ans.: C
Q.470 Conservator in transformer is used
A. to take up expansion of oil due to temp. rise
B. to act as oil storage
C. to better cooling of transformer
D. none of above
Ans.: A
Q.471 If per unit impedances of two transformers are not equal, which of following statement is correct?
A. Transformer will get heated
B. Dead short circuit will occur
C. The power factors of both transformers will be different
D. The transformer with high impedance will share more load
Ans.: D
Q.472 An Autotransformer is preferred over an ordinary two winding transformer due to
A. Safety in operation
B. Availability of tap in secondary winding
C. Isolation between primary and secondary winding
D. Considerable saving in copper when transformation ratio is near to 1
Ans.: D
Q.473 Skew of rotor eliminates
A. Effect of space harmonics
B. Entire effect of crawling
C. Magnetic Noise
D. Vibration due to unequal force developed in motor
Ans.:A
Q.474 It is desirable to eliminate 5th harmonic voltage from the phase voltage of an alternator. The coil should be short pitched by an electrical angle of
A. 30
B. 36
C. 72
D. 18
Ans.: B
Q.475 Leakage reactance of the armature of a salient pole synchronous machine which varies with the position of rotor is due to leakage flux
A. of end connection
B. Which remains within the slot
C. which cones out of slot teeth crosses the air gap and enters the pole faces
D. None of above
Ans.: C
Q.476 A leading power factor load on an alternator implies that the voltage regulating shall be
A. positive
B. Negative
C. zero
D. Any of above
Ans.: B
Q.477 If the field of a synchronous motor is under excited the power factor will be
A. lagging
B. leading
C. unity
D. more than unity
Ans.: A
Q.478 A synchronous motor ill deliver maximum power when
A. load angle is equal to internal angle
B. input power factor is unity
C. load angle is 45
D. load angle is 0
Ans.: A
Q.479 Uneven gap in induction motor is likely to cause
A. Heating of motor
B. Unbalancing of motor shaft
C. Both A and B
D. none of above
Ans.: C
Q.480 An induction motor has synchronous speed of 1500 rpm, what will the slip when it is running on a speed of 1450 rpm?
A. -3.33%
B. +3.33%
C. 4%
D. 6%
Ans.: A