Download PTU B.Tech 2020 March EE 5th Sem 70557 Power Electronics Question Paper

Download PTU (I.K. Gujral Punjab Technical University Jalandhar (IKGPTU) ) BE/BTech EE (Electrical Engineering) 2020 March 5th Sem 70557 Power Electronics Previous Question Paper

1 | M-70557 (S2)-339
Roll No. Total No. of Pages : 02
Total No. of Questions : 09
B.Tech.(EE) (2012 Onwards) (Sem.?5)
B.Tech. (Electrical & Electronics Engg.) (2011 Onwards)
B.Tech.(Electronics & Electrical Engg.) (2012 to 2017)
POWER ELECTRONICS
Subject Code : BTEE-504
M.Code : 70557
Time : 3 Hrs. Max. Marks : 60
INSTRUCTION TO CANDIDATES :
1. SECTION-A is COMPULSORY consisting of TEN questions carrying TWO marks
each.
2. SECTION-B contains FIVE questions carrying FIVE marks each and students
have to attempt any FOUR questions.
3. SECTION-C contains THREE questions carrying TEN marks each and students
have to attempt any TWO questions.

SECTION-A
1. Answer briefly :
a) What is gate triggering? Discuss.
b) Explain why protection of SCR from over voltage is required?
c) Define latching and holding current.
d) What do you mean by power dissipation? Explain.
e) Explain the importance of phase angle control.
f) Draw the Symbol and characteristics of LASCR.
g) Differentiate between forced and natural commutation.
h) Explain the operating principle of a Inverter.
i) Write down the advantages and disadvantages of cycloconverters.
j) What do you mean by voltage commutated chopper? Explain.
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1 | M-70557 (S2)-339
Roll No. Total No. of Pages : 02
Total No. of Questions : 09
B.Tech.(EE) (2012 Onwards) (Sem.?5)
B.Tech. (Electrical & Electronics Engg.) (2011 Onwards)
B.Tech.(Electronics & Electrical Engg.) (2012 to 2017)
POWER ELECTRONICS
Subject Code : BTEE-504
M.Code : 70557
Time : 3 Hrs. Max. Marks : 60
INSTRUCTION TO CANDIDATES :
1. SECTION-A is COMPULSORY consisting of TEN questions carrying TWO marks
each.
2. SECTION-B contains FIVE questions carrying FIVE marks each and students
have to attempt any FOUR questions.
3. SECTION-C contains THREE questions carrying TEN marks each and students
have to attempt any TWO questions.

SECTION-A
1. Answer briefly :
a) What is gate triggering? Discuss.
b) Explain why protection of SCR from over voltage is required?
c) Define latching and holding current.
d) What do you mean by power dissipation? Explain.
e) Explain the importance of phase angle control.
f) Draw the Symbol and characteristics of LASCR.
g) Differentiate between forced and natural commutation.
h) Explain the operating principle of a Inverter.
i) Write down the advantages and disadvantages of cycloconverters.
j) What do you mean by voltage commutated chopper? Explain.
2 | M-70557 (S2)-339
SECTION-B
2. Draw and explain the VI characteristics of a SCR.
3. Describe the working of four quadrant chopper with relevant circuit diagrams and its
operation in all the four quadrants.
4. Explain the operating principle of single phase to single-phase step down cycloconverter
with the help of midpoint configuration for discontinuous load current.
5. Discuss, with the relevant waveforms, Class D type of commutation employed for
thyristor circuits.
6. A single phase 230V, 1kW heater is connected across l-phase, 230V, 50Hz supply
through a SCR. For the firing angle delays of 45 degree and 90 degree, Calculate the
power absorbed in the heater element. Also comment upon the result obtained.

SECTION-C
7. Describe in detail modified McMurray half bridge inverter with appropriate voltage and
current waveforms. Explain its operation by dividing the total commutation interval into
certain well defined modes.
8. Discuss the various Firing circuits of SCR along with their waveforms.
9. Discuss :
a) Two quadrant chopper
b) Dual converter



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.
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