ashishsoniwifistudy

1. The starting current of a 3-ϕ Induction motor is 5times the rated current, while the rated slip is 4%. The

ratio of starting torque to full-load torque is? [ESE 2001]

a) 0.6

b) 0.8

c) 1.0

d) 1.2

2. The rotor power output of 3-phase induction motor is

15 KW. The rotor copper losses at slip of 4% will be?

[ESE 2001]

a) 600 W

b) 625 W

c) 650 W

d) 700 W

3. Which one of the following statements is correct?

[ESE 2004]

a) as speed will reduce

b) its efficiency will improve

c) its power factor will reduce

d) its breakdown torque will reduce

4. Which one of the following is the correct statement?

OR

In a 3-phase induction motor, the resultant flux is of a

constant nature and is? [ESE 2007]a) equal to 𝛟𝐦 where 𝛟𝐦 is maximum flux due to anyphase

b) 1.5 time maximum value of flux due to any

c)𝟑

𝟐times maximum value of flux due to any

d) 𝟑 𝛟𝐦

5. When the applied rated voltage per phase is reduce

to one-half, the starting torque of a three-phase

squirrel cage induction motor becomes? [ESE 2006]

a) ½ of the initial value

b) ¼ of the initial value

c) Twice of the initial value

d) 4 times of the initial value

6. If the full-load speed of a 3-phase, 50 Hz induction

motor is 950 rpm, what is its half-load speed nearly

equal to? [ESE 2007]

a) 1000 rpm

b) 450 rpm

c) 1900 rpm

d) 975 rpm

7. Which one of the following statements is correct? A

smaller air gap in a polyphase induction motor helps

to? [ESE 2004]

a) reduce the chances of crawling

b) increase the starting torque

c) reduce the chance of cogging

d) reduce the magnetizing current

8. The advantage of the double squirrel-cage

induction motor over single cage rotor is that its?

[ESE 2001]

a) efficiency is higher

b) power factor is higher

c) slip is larger

d) starting current is lower

9. What is the frequency of rotor current of a 50 Hz

induction motor operating at 2% slip? [ESE 2007]

a) 1 Hz

b) 100 Hz

c) 2 Hz

d) 50 Hz

10. A 6 pole, 50 Hz, 3 phase induction motor is running

at 950 r.p.m. It has rotor copper loss of 5 kW. The rotor

input will be: [UPRVUNL (AE) 2016]

a) 100 kW

b) 95 kW

c) 10 kW

d) 5.3 kW

11. In AC rotating machines the generated or speed

EMF [RRB SSE 2015]a) leads ϕ by 90°b) lags ϕ by 90°c) is in phase with working fluxd) lags ϕ by 180°

12. The crawling in an induction motor is caused by

[RRB SSE Secundrabad 2015]

a) Improper design of the machine

b) Low voltage supply

c) High loads

d) Harmonics developed in the motor

13. Which of the following motors is represented by the

characteristic curve shown below?

[SSC JE Electrical 2017]

a) D.C. shunt motor

b) D.C. series motor

c) D.C. compound motor

d) Asynchronous motor

14. Rotating magnetic field is produced in a ……..

[RRB SSE 2015]

a) Single-phase induction motor

b) Three-phase induction motor

c) D.C. series motor

d) A.C. series motor

15. The output power of any electric motor is taken

from– [RRB JE 2015]

a) frame

b) commutator

c) coupling mounted on shaft

d) armature

16. If the rotor circuit resistance of a 3 phase induction

motor is increased, then [UPPCL (AE) Electrical 2015]

a) The starting torque will increase but the maximum

torque will remain unchanged

b) Both the starting and the maximum torque will

decrease

c) The starting torque will decrease but the maximum

torque will remain unchanged

d) Both the starting and the maximum torque will

increase

17. The following speed-torque characteristics are

obtained for a 3-phase induction motor. Pick up the

correct method of speed control from the option.

(Output constant) [APGenco-12]

a)𝐕

𝐟control

b)𝐄

𝐟control

c) pole changing with f constant

d) stator voltage control, f constant

18. A 3-phase cage rotor induction motor has its stator

wound for 8 poles. The rotor of this motor can be used

in any other induction motor of the same size and

having [EPDCL-10]

a) 4 poles

b) 8 poles

c) 2 poles

d) any number of poles

19. A 4-pole 3-phase induction motor which has a

rotor current of frequency 3Hz gets supply from a 6-

pole 3-phase alternator running at 600 rpm. At what

speed does the motor operates? [UPPCL (AE) 2016]

a) 810 rpm

b) 750 rpm

c) 720 rpm

d) 1060 rpm

20. maximum internal torque generated in a

Polyphase induction motor cannot be referred as:-

[UPPCL (AE) 2016]

a) Stalling torque

b) Pull-out torque

c) Breakdown torque

d) total torque

21. If rotor speed of an induction motor is 480 rpm and

rotor gross output is 2000W, the magnitude of shaft

torque developed is:- [UPPCL (AE) 2016]

a) 31.14 N-m

b) 39.80 N-m

c) 38.67 N-m

d) 41.89 N-m

22. Sometimes, in a 3-phase induction motor, in order

to improve starting torque– [UPPCL 2016]

a) piece of wood are placed deep inside the rotor

b) copper bars are removed from the rotor

c) Cast Iron bearings are used to support rotor

d) copper bars are placed deep inside the rotor

23. A 3-phase induction motor is running at slip ‘s’. If its

two supply leads are interchanged, then the operating

slip at that instant will be. [DMRC 2016]

a) (2s)

b) (1-s)

c) (2-s)

d) Zero

24. A 3 phase, 50 Hz induction motor draws 50 kW from

the mains. If the stator losses are 2 kW and rotor emf

oscillates at 100 oscillations per minute the rotor

copper losses will be: [LMRC SC/TO 2015]

a) 1.8 kW

b) 1.2 kW

c) 1.9 kW

d) 1.6 kW

25. A star/delta starter of a 3 phase induction motor is

equivalent to an auto transformer starter having a

tapping of: [LMRC SC/TO 2015]

a)𝟏

𝟑

b)𝟑

𝟐

c)𝟏

𝟐

d) 𝟑

26. The rotor reactance per phase, in an induction

motor is– [UPPCL 2016]

a) directly proportional to the square of slip

b) directly proportional to slip

c) inversely proportional to the square of slip

d) inversely proportional to slip

27. A 3-phase delta connected squirrel cage induction

motor when started with a DOL starter has a starting

torque of 600NM. Its starting torque when star delta

starter is used: [DMRC 2016 & Uttarakhand AE Electrical

2013]

a) 600Nm

b) 200Nm

c) 300Nm

d) 1200Nm

28. The main reason for low power factor is the

installation of: [LMRC SC/TO 2015]

a) synchronous motors

b) single phase motor

c) induction motors

d) rectifiers

29. The major disadvantage of DOL starting of

Induction motors is that its application is restricted to–

[UPPCL 2016]

a) low horsepower motors

b) high speed motors

c) high horsepower motors

d) variable speed motors

30. Slip ring motor is preferred over Squirrel Cage

motor when– [UPPCL 2016]

1. high starting torque is required

2. load torque is heavy

3. heavy pull out torque is required

a) Only 3

b) Only 1

c) Only 1 and 2

d) Only 2 and 3

31. Which of the following does not increase/improve

when load on Squirrel Cage induction motor is

increased from No-load to Full-load? [UPPCL 2016]

a) Stator power factor

b) Torque developed by the motor (up to the

magnitude of applied torque)

c) Slip

d) Magnetising component of stator exciting current

32. The torque of an induction motor in synchronous

watt is equal to [MP JE 2016]

a) rotor input

b) stator output

c) stator input

d) watts at rotor speeds

33. The low power factor of induction motor is due to

[UPSSC 2015]

a) rotor leakage reactance

b) stator reactance

c) the reactive lagging magnetizing current necessary

to generate the magnetic flux

d) all of the above

34. In a three phase Induction motor normally

[UPSSC 2015]

a) the rotor rotates in the direction of the rotating

magnetic field

b) The rotor rotates against the direction of the rotating

magnetic field

c) the rotor rotates depending upon the supply given

to it

d) The direction of rotor rotation does not depend

upon the phase sequence of the stator supply

35. The stator of 5 H.P. induction motors is provided with

[IOF 2014]

a) Open slots with tapered teeth

b) Open slots with parallel teeth

c) Closed slots with parallel teeth

d) Semi closed slots with parallel teeth

36. 3-phase, 50 Hz, 500 V induction motor develops 20

HP at slip of 5%. Mechanical losses are 1 HP, and stator

loss is 1 kW. The efficiency will be [Uttrakhand 2013]

a) 95.3%

b) 90.5%

c) 91.3%

d) 85.3%

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SSC JE-2019

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(28) In a steam power plant…………heats the feed water on its way to the boiler by

delivering heat from the flue gases: -

(A) Superheater (B) Economizer

(B) Preheater (D) Turbine

(29) Power generation of thermal power plants is based on: -

(A) Rankine cycle

(B) Otto cycle

(C) Diesel cycle

(D) Carnot cycle