AC Motors 5

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Objective Questions with Answers for Electrician and Wireman: AC Motors 5

Subject: AC Motors 5

Part 5: Objective questions and answers of AC Motors


Q1. Which is the application of single quadrant loads operating in first quadrant in drives?

a) Hoists

b) Elevators

c) Conveyors

d) Centrifugal pumps


Q2. What is the disadvantage of DC drive?

a) Not suitable for high speed operation

b) More complex with a single power conversion

c) More expensive than AC drive for high capacity motor

d) Installation of DC drives is more complicated


Q3. Which is the correct sequence operation of key button in BOP of AC drive to change the direction of rotation?

a) Press ON – REV -ON

b) Press OFF – REV – ON

c) Press ON – OFF – REV -ON

d) Press ON -REV – OFF -ON


Q4. Which is proportional to the torque in D.C motor?

a) Back e.m.f

b) Field current

c) Terminal voltage

d) Armature current


Q5. What is the function of VSI drives?

a) Converts A.C to D.C

b) Converts A.C to A.

c) Converts D.C to A.C

d) Converts D.C to D.C


Q6. How the base speed of D.C shunt motor can be increased by using D.C drive?

a) By reducing the field current

b) By increasing the field current

c) By increasing the supply voltage

d) By reducing the armature voltage


Q7. Which type of plier is used for removing the sheath and insulation from cable?

a) Combination pliers

b) Flat nose pliers

c) Diagonal cutting pliers

d) Round nose pliers


Q8.Which type of tool is used for holding small objects in places where fingers cannot reach?

a) Flat nose pliers

b) Long nose pliers

c) Side cutting pliers

d) Round nose pliers


Q9. How will you diagonise the victim is suffering under cardiac arrest?

a) Gets pain in spinal guard

b) Mouth will be closed tightly

c) Heavy swelling on his stomach

d) Appears blue colour around his lips


Q10. The concept of MHD generation depends much more on the……. Of the gas in the duct.

a) Permeability

b) Permittivity

c) Conductivity

d) None of these


Q11. The thickness of the metal used in sheet metal works above 5 mm is called as:

a) Sheets

b) Plates

c) Strips

d) Foils


Q12. What is the advantage of AC drive compared to DC drive?

a) Requires less space

b) Installation and running cost is less

c) Fast response and wide speed range of control

d) Power circuit and control circuits are simple


Q13. What is the function of Field Supply Unit (FSU) in DC drive?

a) Produces required firing current to the firing circuit

b) Provides variable voltage to the field winding of motor

c) Provides a constant voltage to the field winding of motor

d) Provides a constant voltage to the armature of the motor


Q14. What is the purpose of LCD in Basic Operator Panel (BOP) in AC drive?

a) Indicate the status of drive

b) Monitor the parameter of AC drive

c) Indicate the display error in reading

d) Indicate the incorrect operation of BOP


Q15. What is the purpose of PROG / DATA button in BOP of AC drive?

a) To change the parameter setting

b) To store the entered data and factory stored data

c) To display the data direction of rotation forward / REV

d) To display the data status of frequency and current


Q16. What is IGBT in VF drive?

a) Inverter switching device

b) D.C bus switching device

c) Rectifier switching device

d) Field supply switching device


Q17. Why the A.C drives are mostly used in process plant?

a) Easy to operate

b) Robust in construction

c) Very high starting torque

d) Maintenance free long life


Q18. How the constant torque can be obtained from armature and field-controlled drives?

a) By reducing the field current

b) By increasing the field current

c) By reducing the armature current

d) By controlling the armature voltage


Q19. The reactance of a 2 henry choke coil at 100 Hz is:

a) 100 ohm

b) 216 ohm

c) 718 ohm

d) 1256 ohm


Q20. The single phase domestic AC supply voltage in India is:

a) 110 V

b) 230 V

c) 440 V

d) 550 V


Part 5: Objective questions and answers of AC Motors


Q1. Answer d

Q2. Answer a

Q3. Answer a

Q4. Answer d

Q5. Answer a

Q6. Answer a

Q7. Answer: c

Q8. Answer: b

Q9. Answer: d

Q10. Answer c

Q11. Answer b

Q12. Answer b

Q13. Answer c

Q14. Answer b

Q15. Answer b

Q16. Answer a

Q17. Answer d

Q18. Answer d

Q19. Answer d

Q20. Answer b

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