Download PTU (I.K.Gujral Punjab Technical University (IKGPTU)) B-Tech (Bachelor of Technology) (EEE)- Electrical And Electronics Engineering 2020 December 4th Sem Asynchronous Machines Previous Question Paper
Roll No.
Total No. of Pages : 02
Total No. of Questions : 18
B.Tech. (EE) (2012 Onwards)/(Electrical & Electronics)(2011 & 2012
Batch)/(Electrical Engineering & Industrial Control)(2012 to 2017)/
(Electronics & Electrical)(2012 Ba tch) (Sem.?4)
ASYNCHRONOUS MACHINES
Subject Code : BTEE-401
M.Code : 57104
Time : 3 Hrs. Max. Marks : 60
INST RUCT IONS T O CANDIDAT ES :
1 .
SECT ION-A is COMPULSORY cons is ting of TEN questions carrying TWO marks
each.
2 .
SECT ION-B c ontains F IVE questions c arrying FIVE marks eac h and s tud ents
have to atte mpt any FOUR q ues tions.
3 .
SECT ION-C contains THREE questions carrying T EN marks e ach and s tudents
have to atte mpt any T WO questio ns.
SECTION-A
Answer briefly :
1.
"The rotating fields of the stator and rotor are stationary with respect to each other".
Justify the statement.
2.
Why is the efficiency of a 3-phase induction motor less than that of a 3-phase
transformer?
3.
Explain the function of two stator windings in a single-phase induction motor.
4.
Draw the neat diagrams of single-phase capacitor.-start capacitor-run induction motor.
5.
Name the four types of starters used for 3-phase induction motor.
6.
Why does a 3-phase induction motor always run at a speed less than the synchronous
speed?
7.
What is the effect of introducing resistance in the rotor circuit of a 3-phase induction
motor?
8.
State the condition for maximum torque in a 3-phase induction motor.
9.
A voltmeter gives 120 oscillations per minute when connected to the rotor of an induction
motor. Find the slip of the motor. The stator frequency is 50 Hz.
10. In case of induction motors, explain why the air gap length is kept as small as is
mechanically possible?
1 | M Code 57104 (S2)-691
SECTION-B
11. Derive the condition for maximum torque in a 3-phase induction motor.
12. Explain the principle of operation of a self-excited 3-phase induction generator. Give the
condition under which this generator may fail to build-up.
13. When main winding of a single-phase induction motor is connected to 200 V, 50 Hz
source, it takes a current 50 A at an angle of -60? at standstill position. Find the rotor
circuit parameters. Neglecting stator leakage impedance and magnetizing current.
14. Explain how the speed of a 3-phase induction motor can be controlled by injecting a
voltage in the rotor circuit of 3-phase induction motor.
15. Describe the construction and working of universal motor.
SECTION-C
16. Explain how the stationary, pulsating m.m.f. wave of a single phase induction motor can
be considered as equivalent to two equal but oppositely rotating m.m.f. waves.
17. Describe the constructional features and working of a single-stack 3-phase 6/4-pole
variable reluctance stepping motor.
18. The starting torque of 100 Nm is developed in a 3-phase squirrel-cage induction motor by
an auto-transformer starter with a tapping 40%. Find the starting torque, if the tapping of
the auto-transformer is changed to 80%.
NOTE : Disclosure of Identity by writing Mobile No. or Making of passing request on any
page of Answer Sheet will lead to UMC against the Student.
2 | M Code 57104 (S2)-691
This post was last modified on 13 February 2021