ashishsoniwifistudy

1. If the stator winding of a three-phase induction

motor is delta connected, the rotor winding.

[Uttrakhand 2013]

a) should be delta connected

b) should be star connected

c) should not be delta connected

d) may be delta or star connected

2. If static voltage of a squirrel cage induction motor is

reduced to 50 percent of its rated value, torque

developed is reduced by how many percentage of its

full load value? [SSCJE 2015]

a) 50%

b) 75%

c) 25%

d) 57.7%

3. How many different speeds can be obtained in

cascade control of two induction motors? [SSCJE 2007]

a) 2

b) 4

c) 8

d) 16

4. Which of the following braking is not suitable for

motors? [SSCJE 2015]

a) Plugging

b) Dynamic braking

c) Friction braking

d) Regenerative braking

5. In a 4-phase induction machine, motoring

generating and braking operations take place in the

range of slip “S” is? [ESE 2010]

a) 1>S>0, 0>S>–2 and S>1

b) S>1, 1>S>–1 and 1>S>–1

c) S>1, 0>S>–1 and 1>S>0

d) 0>S>–1, S>1 and 1>S>0

6. Consider the following statements?

Skewing of rotor slots in a 3-phase induction motor

(cage rotor) may? [ESE 2008]

1. introduce additional leakage reactance

2. eliminate slot harmonis

Which of these statements is/are correct?

a) 1 only

b) 2 only

c) Both 1 and 2

d) Neither 1 nor 2

7. If the starting torque of a 3 phase induction motor is𝐓𝐬𝐭 for DOL starting, that for star-delta starting of the

same motor is [SSCJE 2012]a) 𝐓𝐬𝐭/𝟑

b) 𝐓𝐬𝐭/ 𝟑

c) 𝟑 𝐓𝐬𝐭/𝐓d) 𝟑𝐓𝐬𝐭

8. How many watt-seconds are supplied by a motor

developing 2 H.P. (British) for 5 hours? [SSCJE 2013]

a) 𝟐. 𝟔𝟖𝟓𝟔 × 𝟏𝟎𝟕 watt-seconds

b) 𝟒. 𝟒𝟕𝟔 × 𝟏𝟎𝟓 watt-seconds

c) 𝟐. 𝟔𝟒𝟔 × 𝟏𝟎𝟕 watt-seconds

d) 𝟔. 𝟑𝟗𝟒𝟑 × 𝟏𝟎𝟔 watt-seconds

9. V/f is maintained constant in the following case of

speed control of induction motor: [DMRC 2014]

a) Below base speed with voltage control

b) Below base speed with frequency control

c) Above base speed with frequency control

d) None of these

10. In a three-phase induction motor, the rotor field

runs at the following speed with respect to the stator

structure: [DMRC 2014]

a) At synchronous speed in the direction of stator field

b) At a slip speed in the direction of stator speed

c) At synchronous speed in a direction opposite to that

of stator field

d) At zero speed

11. The rated torque at starting with minimum possible

stator current of a three-phase squirrel cage induction

motor can be achieved by: [DMRC 2015]

a) Changing stator voltage

b) Changing frequency of stator supply

c) Changing frequency and voltage of stator supply

d) Changing poles on stator

12. Starting torque of a three-phase squirrel cage

induction motor at rated voltage is: [DMRC 2015 &

F.C.I. 2015]

a) 30% to 40% of the rated torque

b) The rated torque

c) 100% to 200 of the rated torque

d) 5 to 7 times of the rated torque

13. Which of the following methods could be used to

start a Three-phase cage-type induction motor?

[UPRVUNL 2014]

I. Direct-on-line starting

II. Auto-transformer starting

III. Star-delta starting

Chose the correct answer from the options given

below.

a) Only I and II

b) Only II and III

c) I, II and III

d) Only I and III

14. Which of the following statements is correct

regarding the actual voltage which is used for setting

up the useful flux in the air gap of a 3-phase induction

motor? [UPRVUNL 2014]

a) It is equal to applied voltage

b) It is greater than applied voltage

c) It is less than applied voltage

d) it is equal to rotor induced emf

15. When the load on an induction motor is increased

from no load to full load: [UPRVUNL 2014]

a) Both slip and power factor decrease

b) Both slip and power factor increase

c) Slip decreases and power factor increases

d) Slip increases and power factor decreases

16. If an induction motor is to be run on unbalanced

supply then it should run at: [UPRVUNL 2015]

a) Lower loads

b) Higher loads

c) Low speeds

d) Higher speeds

17. Unbalance in shaft of an induction motor occurs

due to: [UPRVUNL 2015]

a) Non uniform air gap

b) Overheating of the winding

c) Slip rings design

d) Rugged construction

18. Which of the following is correct with respect to the

speed of cage rotor induction motor?

The speed of 3-phase cage rotor induction motor

depends upon. [UPRVUNL 2015]

A. Number of poles

B. Frequency of supply

C. Input voltage

a) Only A

b) Only B

c) Only B and C

d) Only A and B

1. An induction motor has a starting torque 300 Nm

when started by direct switching. If a star delta starter

is used for starting, the starting torque will be

[BSNL TTA (JE) 2015]

a) 300 Nm

b) 100 Nm

c) 173.2 Nm

d) 900 Nm

2. Almost 90% of the induction motors are squirrel cage

type because [BSNL TTA 2016]

a) They have better starting torque

b) Their speed an be controlled very smoothly over a

wide range

c) They can run both at lagging and leading power

factors

d) They have the simplest and most rugged

construction

3. A three phase Induction motor always [UPSSSC 2015]

a) Works at lagging power factor

b) Works at leading power factor

c) Works at maximum (i.e. unity) power factor

d) The power factor keeps changing with the load

4. The speed of a motor generator set consisting of 6-

pole induction motor and a 4-pole dc generator fed

from a 3 phase 50 Hz supply is– [BSNL TTA 2016]

a) 1000

b) 600

c) 1500

d) 3000

5. Standard Motor Starter supplies ____ initial voltage

for proper starting of the motor. [BSNL TTA (JE) 2016]

a) Higher

b) Constant

c) Normal

d) Lower

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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