HPCL Electrical-Engineering-EE

                                    HPCL Placement Paper – Electrical Engineering

1. State the range of generation voltage.
a. Between 400 KV and 700 KV
b. Between 11 KV and 33 KV
c. Between 132 KV and 400 KV
d. None of the above

2. Choose which of the following option falls true for hysteresis motor.
a. Needs Dc excitation
b. Is not a self – starting motor
c. Is a constant speed motor
d. Cannot be run in reverse speed

3. Which heating method is independent of supply frequency?
a. Dielectric heating
b. Electric arc heating
c. Induction heating
d. Electric resistance heating

4. What is the maximum torque in a 3 phase induction motor?
a. Does not depend on rotor resistance
b. Is proportional to rotor resistance
c. None of the above

5. What is the power factor of a squirrel cage induction motor?
a. Low at heavy load only
b. Low at light load only
c. Low at light and heavy load only
d. Low at rated load only

6. Choose the correct option for identifying the two windings of a transformer?
a. Not linked at all
b. Conductively linked
c. Electrically linked
d. Inductively linked

7. Fill in the blanks
In a stepper motor the angular displacement ___
a. It cannot be used for positioning of work tables and tools in NC machine
b. Can be precisely controlled
c. It cannot be readily interfaced with micro - computer based controller
d. The angular displacement cannot be precisely controlled

8. The purpose of inducing emf in the primary of a transformer _________
a. Leads the flux by 90 degree
b. Lags behind the flux by 90 degree
c. Is in phase with the flux
d. Is in phase opposition to that of flux

9. Which motor will you choose which can operate in both lagging as well as leading power factors?
a. Synchronous motor
b. Squirrel cage motor
c. DC shunt motor
d. Wound rotor induction motor

10. What will be the voltage regulation of a full load and 0.80 power factor lagging load transformer when a two winding single phase transformer has a voltage regulation of 4.5% at full load and unity power factor?
a. 4.5% or more
b. Less that 4.5%
c. 4.5%
d. More than 4.5 %

11. What is the armature mmf in a D.C machine?
a. Rotating w.r.t field
b. Stationary w.r.t armature
c. Rotating w.r.t brushes
d. Stationary w.r.t field

12. What will be the output voltage of a transformer if it is primarily energised from a square wave voltage source?
a. A pulse wave
b. A square wave
c. A sine wave
d. A triangular wave

13. How will a motor react if salient pole is running synchronously at no load and its field current is switched off?
a. Come to a halt
b. Continue to run at a speed slightly less than the synchronous speed
c. Continue to run at synchronous speed
d. Continue to run at a speed slightly more than the synchronous speed

14. Why should you always start the D.C series motor with load?
a. It will fail to start
b. It will not develop high starting torque
c. At no load, it will rotate at dangerously high speed
d. All the above mentioned are true

15. Which is the most suitable servomotor for low power application?
a. A DC shunt motor
b. A DC series motor
c. An AC two – phase induction motor
d. An AC series motor

16. What will you use to take out the current from the stator of an alternator?
a. Commutator segments
b. Slip rings
c. Carbon brushes
d. Solid connections

17. When will be the voltage zero in a transformer?
a. Leading p.f
b. Zero p.f leading
c. Unity p.f
d. Lagging p.f

18. When the relative speed between the magnetic fields of stator and rotor does is zero under steady state operation?
a. Synchronous machine
b. DC machine
c. Single phase induction machine
d. 3 phase induction machine
e. All of the above are true

19. What shall be the secondary output voltage if the primary winding of a 220/6V, 50 Hz transformer is energised by a 110V, 60 Hz supply?
a. 3.0 V
b. 3.6 V
c. 2.5 V
d. 6.0 V

20. What is the mechanical power developed in terms of air gap power Pg in a 3 phase induction motor running at slip ‘s’?
a. (s-1) Pg
b. Pg/1-S
c. 1-SPg-Answer
d. S.Pg

21. The electromagnetic torque developed in proportional to what in a D.C series motor?
a. 1a
b. 12a-Answer
c. 1/1a
d. 1/12a

22. What is the frequency of the rotor current in a 3 phase 50 Hz, 4 pole induction motor at full load?
a. 2 Hz
b. 20 Hz
c. Zero
d. 50 Hz

23. What does the damper winding produce when a synchronous motor is running at a synchronous speed?
a. Eddy current torque
b. Damping torque
c. No torque
d. Torque aiding the developed torque