ELECTRICIAN 2nd YEAR MODULE – AC / DC Motor Drives ONLINE TEST

Question 1 of 33

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

Produces required firing current to the firing circuit

Provides variable voltage to the field winding of motor

Provides a constant voltage to the armature of the motor

Provides a constant voltage to the field winding of motor

Question 1 of 33

Question 2 of 33

2. Why are A.C drives better suited for high speed operation?

High starting torque

Robust in construction

No brushes and commutation

Having lighter gauge winding

Question 2 of 33

Question 3 of 33

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

By reducing the field current

By increasing the field current

By reducing the armature voltage

By increasing the supply voltage

Question 3 of 33

Question 4 of 33

4. Which drive is classified according to mode of operation?

Continuous duty drive

Individual drive

Manual drive

Group drive

Question 4 of 33

Question 5 of 33

5. What is the purpose of JOG key in control panel of D.C drive?

Restart the motor

Reverse the direction of motor

Stop the motor

Inching operation

Question 5 of 33

Question 6 of 33

6. Which control system consumes very low power for motion control in AC and DC motors?

Field control

Armature control

Drives control

Voltage control

Question 6 of 33

Question 7 of 33

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

Back e.m.f

Field current

Armature current

Terminal voltage

Question 7 of 33

Question 8 of 33

8. What is the name of the characteristic curve in D.C drive?

Field current Vs armature current characteristic

Speed Vs armature current characteristic

Torque Vs field current characteristic

Speed Vs torque characteristic

Question 8 of 33

Question 9 of 33

9. Which device controls the speed of A.C motor in A.C drive?

COMMS technology box

Field supply unit (FSU)

Microprocessor based electronic device

Speed feedback technology box

Question 9 of 33

Question 10 of 33

10. How can constant torque be obtained from armature and field controlled drives?

By controlling the armature voltage

By reducing the field current

By reducing the armature current

By increasing the field current

Question 10 of 33

Question 11 of 33

11. What is the function of power controller in drive circuits?

It reduce motor current during transient operation

It detects the overloading condition of motor

It maintain the torque at low voltage conditions

It sounds an alarm in no load conditions

Question 11 of 33

Question 12 of 33

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

Centrifugal pumps

Conveyors

Elevators

Hoists

Question 12 of 33

Question 13 of 33

13. What is the disadvantage of DC drive?

Not suitable for high speed operation

More complex with a single power conversion

More expensive than AC drive for high capacity motor

Installation of DC drives is more complicated

Question 13 of 33

Question 14 of 33

14. What is the full form of B.O.P in D.C drive?

Bridge Operation Panel

Basic Operation Programme

Basic Operational Panel

Bridge Operator Programme

Question 14 of 33

Question 15 of 33

15. Which type of sensing unit is employed in drive systems?

Resistance temperature detector

Opto coupler

Photo voltaic cell

Speed sensing

Question 15 of 33

Question 16 of 33

16. What is the main use of A.C drive?

Control stepless speed in motors

Group drive motors

High starting torque

Interlocking system in industries

Question 16 of 33

Question 17 of 33

17. Which control system is used for Eddy current drives?

Rectifier controller

DC chopper controller

Slip controller

AC voltage controller

Question 17 of 33

Question 18 of 33

18. What is IGBT in VF drive?

Rectifier switching device

Inverter switching device

D.C bus switching device

Field supply switching device

Question 18 of 33

Question 19 of 33

19. What is the purpose of LCD on basic operator panel in D.C drive?

Display the speed

Display availability of supply

Indicate the fault

Monitor the parameter

Question 19 of 33

Question 20 of 33

20. Why are A.C drives mostly used in process plants?

Maintenance free long life

Very high starting torque

Robust in construction

Easy to operate

Question 20 of 33

Question 21 of 33

21. Which is the classification of drive according to dynamics and transients?

Variable position control drive

Short time duty drive

Automatic control drive

Intermittent duty drive

Question 21 of 33

Question 22 of 33

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

Requires less space

Installation and running cost is less

Fast response and wide speed range of control

Power circuit and control circuits are simple

Question 22 of 33

Question 23 of 33

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

Press ON → REV → OFF → ON

Press ON → OFF → REV → ON

Press OFF → REV → ON

Press ON → REV → ON

Question 23 of 33

Question 24 of 33

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

To display the data direction of rotation forward/REV

To store the entered data and factory stored data

To display the data status of frequency and current

To change the parameter setting

Question 24 of 33

Question 25 of 33

25. What is the function of IGBT in AC drive?

Stabilize the output voltage from the rectifier

Smoothening incoming A.C supply

Controls the power delivered to the motor

Converts incoming A.C power into D.C power output

Question 25 of 33

Question 26 of 33

26. What is the name of the component marked as 'X' in the block diagram of AC drive?

Inverter

A.C motor

D.C bus

Rectifier

Question 26 of 33

Question 27 of 33

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

Monitor the parameter of AC drive

Indicate the display error in reading

Indicate the incorrect operation of BOP

Indicate the status of drive

Question 27 of 33

Question 28 of 33

28. Which type of machine in industries is provided with multi-motor electric drive?

Shearing machine

Heavy duty electric drilling machine

Air Compressor

Rolling machine

Question 28 of 33

Question 29 of 33

29. What is the function of VSI drives?

Converts D.C to A.C

Converts D.C to D.C

Converts A.C to D.C

Converts A.C to A.C

Question 29 of 33

Question 30 of 33

30. Which power modulator is used in the electric drive system?

Cyclo converters

Frequency multiplier

Phase sequence indicator

Servo controlled voltage stabilizer

Question 30 of 33

Question 31 of 33

31. What is electric drive?

A device converts A.C to D.C supply

A device used as prime mover for generator

A machine converts mechanical energy into electrical

An electro mechanical device for controlling motor

Question 31 of 33

Question 32 of 33

32. Why is it necessary to keep V/F ratio constant in a drive?

Maintain the speed of motor constant

Maintain the rated torque at all speeds

Keep the stator flux maximum

Maintain the rotor current minimum

Question 32 of 33

Question 33 of 33

33. What is the reason for using shielded cable for connecting low level signal circuits in DC drives?

Easy for connection

Eliminates the electrical interference

Good appearance

Protects from mechanical injuries

Question 33 of 33