Induction Motors

#1. 1

star delta starter

auto transformer starter

rotor resistance starter

DOL starter

#2. 1

less than 10 HP

greater than 10 HP

greater than 15 HP

less than 5 HP

#3. 1

300 rpm

500 rpm

600 rpm

800 rpm

120x 50/10=800

#4. 1

0

0.5

1

1.2

#5. 1

rotor copper loss x rotor power input

rotor copper loss /rotor power input

rotor power input x rotor /core loss

rotor core loss/rotor copper loss

#6. 1

ventillation

for holding armature in positions

protection of hole machine

avoid noise

#7. 1

ac only

dc only

ac or dc

none of these

#8. Rotor speed of 3 phase 4 pole 50Hz induction motor is….?

1500 rpm

1440 rpm

1540 rpm

1600 rpm

#9. Stray losses are….?

copper loss

iron loss

magnetic and mechanical loss

frictional loss

#10. Stroboscopic method is used to find ……. of an induction motor?

torque

slip

speed

efficiency

#11. Frequency of rotor current of an induction motor?

slip

slip x frequency of current

speed x slip

frequency of stator current

#12. Which of the motor is not self starting?

universal motor

DC series motor

DC shunt motor

single phase induction motor

#13. Abnormal rubbing sound of induction motors can be prevented by….?

regular starter check

proper & regular lubrication

replacing winding regularly

claening the rotor regularly

#14. Star delta starter has an advantage of….?

high starting current

low starting current

slow rating

high starting torque

#15. In a three phase induction motor crawling happens at…?

any speed

no load speed

odd multiples of fundamental

even multiples of fundamental

#16. In a capacitor start single phase induction motor, the current in the…?

supply lines leads the voltage

starting winding laggs the voltage

main winding laggs the voltage

starting winding leads the voltage

#17. The frame of an induction motor is made by….?

silicon steel

closed grained cast iron

aluminium

stainless steel

#18. The ststor core of an induction motor is laminated to avoid….?

hystersis loss

copper loss

eddy current loss

frictional loss

#19. In synchronous machine shaft is made up of…?

cast iron

copper

stainless steel

mild steel

#20. At starting, the slip of three phase induction motor is…?

0

0.5

1

less than zero

#21. The starting torque of a squirrel cage induction motor is….?

very low

very large

zero

slightly more than full load torque

#22. For a slip ring induction motor, rotor resistance is added then…?

starting torque decrease

starting current increase

starting torque increase

starting speed decrease

#23. The starting torque of 3 phase induction motor is varies with….?

speed

voltage

square of the voltage

current

#24. In an induction motor what is the ratio of rotor copper loss and rotor input?

1

s

1/s

(1-s)

#25. The losses that occur in induction motor are…?

stator copper losss

rotor copper losss

iron loss

mechanical & frictional loss

all the above

#26. The crawling in induction motor is caused by…?

high starting current

high torque

harmonics developed in the motor

high voltage supply

#27. An increse in number of poles of an induction motor results in…?

decrease in maximum power factor

increase in maximum power factor

cannot change power factor

#28. In induction motor percentage slip is maximum at….?

low speed

standstill condition

medium speed

synchronous speed

#29. Rheostat method of speed control of induction motor is used in…..?

slip ring induction motor

squirrel cage induction motor

double cage induction motor

all the above

#30. In squirrel cage induction motor, the rotor conductors are…?

open circuited

short circuited via end ring

short circuited via external reactance

short circuited via external resistance

#31. A 4 pole 3 phase induction motor runs at 1440 rpm on a 50Hz supply. find the slip speed?

2940 rpm

60 rpm

20 rpm

1500 rpm

120f/p= 120x 50/4 =1500

slip speed = 1500 – 1440 = 60 rpm

#32. In a single phase induction motor, speed sensitive centrifugal switch is connected in ….. winding?

parallel with main

series with main

parallel with starting

series with staarting

#33. In a single phase induction motor at start, the two revolving fields produce…..?

unequal torque in the rotor conductors

no torque in the rotor conductors

equal and opposite torque in the rotor conductors

equal torque in the same direction in rotor conductors

#34. In a single phase induction motor at start, the two revolving fields produce…..?

unequal torque in the rotor conductors

no torque in the rotor conductors

equal and opposite torque in the rotor conductors

equal torque in the same direction in rotor conductors

#35. Circle diagram of induction motor can be used to determine its….?

power factor

efficiency

slip

all the above

#36. The power factor of an induction motor at full load is likely to be….?

unity

0.85 lead

0.85 lag

0.5 lag

#37. If the load on an induction motor is increased from no load to full load, its slip and the power factor ill be….?

decrease, decrease

increase, increase

decrease, increase

increase, decrease

#38. In an induction motor, if the air gap is increased….?

speed will reduce

efficiency will improve

power factor will be lowered

break down torque will reduce

#39. In double cage induction motor, the inner cage is….?

low resistance & low leakage reactance

high resistance & highleakage reactance

low resistance & high leakage reactance

high resistance & low leakage reactance

#40. Skewing of induction motor, is to reduce…?

eddy current

noise & vibrations

hysteresis current

none of the above

#41. The squirrel cage type rotor is used in….?

shunt motor

shunt generator

alternator

induction motor

#42. The efficiency of a three phase induction motor is approximately proportional to…?

N

S

(1-S)

Ns

#43. To change DOR of the repulsion motor is…?

To shift brush position

To interchange phase and neutral

To varying the frequency

None of these

Induction Motors

#1. 1

#2. 1

#3. 1

#4. 1

#5. 1

#6. 1

#7. 1

#8. Rotor speed of 3 phase 4 pole 50Hz induction motor is….?

#9. Stray losses are….?

#10. Stroboscopic method is used to find ……. of an induction motor?

#11. Frequency of rotor current of an induction motor?

#12. Which of the motor is not self starting?

#13. Abnormal rubbing sound of induction motors can be prevented by….?

#14. Star delta starter has an advantage of….?

#15. In a three phase induction motor crawling happens at…?

#16. In a capacitor start single phase induction motor, the current in the…?

#17. The frame of an induction motor is made by….?

#18. The ststor core of an induction motor is laminated to avoid….?

#19. In synchronous machine shaft is made up of…?

#20. At starting, the slip of three phase induction motor is…?

#21. The starting torque of a squirrel cage induction motor is….?

#22. For a slip ring induction motor, rotor resistance is added then…?

#23. The starting torque of 3 phase induction motor is varies with….?

#24. In an induction motor what is the ratio of rotor copper loss and rotor input?

#25. The losses that occur in induction motor are…?

#26. The crawling in induction motor is caused by…?

#27. An increse in number of poles of an induction motor results in…?

#28. In induction motor percentage slip is maximum at….?

#29. Rheostat method of speed control of induction motor is used in…..?

#30. In squirrel cage induction motor, the rotor conductors are…?

#31. A 4 pole 3 phase induction motor runs at 1440 rpm on a 50Hz supply. find the slip speed?

#32. In a single phase induction motor, speed sensitive centrifugal switch is connected in ….. winding?

#33. In a single phase induction motor at start, the two revolving fields produce…..?

#34. In a single phase induction motor at start, the two revolving fields produce…..?

#35. Circle diagram of induction motor can be used to determine its….?

#36. The power factor of an induction motor at full load is likely to be….?

#37. If the load on an induction motor is increased from no load to full load, its slip and the power factor ill be….?

#38. In an induction motor, if the air gap is increased….?

#39. In double cage induction motor, the inner cage is….?

#40. Skewing of induction motor, is to reduce…?

#41. The squirrel cage type rotor is used in….?

#42. The efficiency of a three phase induction motor is approximately proportional to…?

#43. To change DOR of the repulsion motor is…?

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