PTU B.Tech 3D EEE 4th Semester May 2019 57104 ASYNCHRONOUS MACHINES Question Papers

PTU Punjab Technical University B-Tech May 2019 Question Papers 4th Semester Electrical and Electronics Engineering (EEE)-EE-Electrical Engineering

Roll No.
Total No. of Pages : 02
Total No. of Questions : 09
B.Tech.(EE) (2011 Onwards)/Electrical & Electronics/Electronics & Electrical)
(2011 &2012 Batch)/
(Electrical Engineering & Industrial Control) (2012 Onwards)
(Sem.?4)
ASYNCHRONOUS MACHINES
Subject Code : BTEE-401
M.Code : 57104
Time : 3 Hrs. Max. Marks : 60
INSTRUCTION TO CANDIDATES :
1.
SECTION-A is COMPULSORY consisting of TEN questions carrying T WO marks
each.
2.
SECTION-B contains FIVE questions carrying FIVE marks each and students
have to attempt any FOUR questions.
3.
SECTION-C contains T HREE questions carrying T EN marks each and students
have to attempt any T WO questions.

SECTION-A
1.
Answer briefly :

a. Define slip of an induction motor.

b. Explain slip frequency of a 3-phase induction motor.

c. Why an induction motor operates at a very low power factor under no-load?

d. Why an induction motor cannot run at synchronous speed?

e. Write two application of single-phase induction motor.

f. Why starting current is high for an induction motor?

g. Why airgap between stator and rotor of induction motor is very small?

h. If a single-phase induction motor is started with auxiliary winding open, what will


happen?

i. How direction of rotation of a three-phase induction motor can be reversed?

j. Write the difference between a squirrel cage and slip ring induction motor.
1 | M Code 57104 (S2)-180

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SECTION-B
2.
Discuss losses in a 3-phase induction motor.
3.
Sketch and explain toque-slip characteristics of 3-phase induction motor.
4.
Explain the starting of squirrel cage induction motor by using Direct-on-line method.
5.
Explain how higher starting torque can be obtained in :

a. Squirrel cage induction motor

b. Wound rotor induction motor.
6.
Explain how rotating torque is generated in a single-phase induction motor.

SECTION-C
7.
Write the constructional features, working principle and applications of single-phase
reluctance motor.
8.
A 230V, 380W, 60 Hz, 4-pole, single phase induction motor gave the following test
results :

No-load test : 230V, 84W, 2.8A

Blocked-rotor test : 110V, 460W, 6.2A

The stator winding resistance is 4.5 ohms and during the blocked rotor test, the auxiliary
winding is open. Determine the equivalent circuit parameters and draw the equivalent
circuit.
9.
Describe the methods of speed control of three phase induction motor.




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)-180

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