B.Tech-B.Tech Electrical and Electronics Engineering 5th Sem Power Electronics - III 5E3123(Rajasthan Technical University-2012)
5E3123
B.Tech. V Sem.(MainIBack) Exam. Dec. 2012
Electrical Engineering
5 EEl Power Electronics - III
Common With Electrical & Electronics
Time: 3 Hours
Maximum Marks: 80
Min. Passing Marks : 24
UNIT- I
Q.1 (a) Explain and draw the switching characteristics of the Gate turn - off thyristor. [8]
(b) What is hard fIring? What are its advantages? Draw a typical wave form for gate current for a thyristor? [8]
OR
Q.1. (a) Write various factors which influence the turn on time of thyristor. Explain how the turn - on time can be minimized. [8]
(b) Explain and draw the switching characteristics of the power IGBT. [8]
UNIT -II
Q.2. (a) Explain the parallel operation of thyristor. How SCRs suffer from unequal voltage distribution across them during their turn-on and turn-off processes? [8]
(b) Explain the significance of di / dt and dv / dt in SCRs. [8]
OR
Q.2. (a) Explain the working of UJT relaxation oscillator triggering circuit for thyristor along with circuit diagram and related waveforms. [8]
(b) Explain and draw the switching characteristics of the SCR. [8]
UNIT-III
Q.3 . (a) Describe working of a single - phase full converter with RL load through the waveforms of supply voltage, load voltage, load current and voltage across thyristor. Also, derive expressions for load voltage and input power factor. [8]
(b) Explain principle of operation of single phase dual converter with circulating current in detail. [8]
OR
Q3 (a) Describe the working of a single - phase one pulse converter with RL load through the waveforms of supply voltage, load voltage, load current and voltage across thyristor. Also, derive expressions for load voltage and input power factor. [8]
(b) Explain principle of operation of three phase dual converter without circulating current in detail. [8]
UNIT-IV
Q.4. (a) Describe the working of a single - phase half controlled converter with RL load through the waveforms of supply voltage, load voltage, load current and voltage across thyristor. Also, derive expressions for load voltage and input power factor. [8]
(b) Explain Extinction angle control technique of power factor improvement along with cricuit diagram and waveforms. [8]
OR
Q.4. (a) Explain with circuit diagram and related waveforms, effect of source inductance on the performance parameters of two pulse full converter. [8]
(b) Explain symmetrical angle control technique of power factor improvement along with circuit diagram and waveforms. [8]
UNIT-V
Q.5. (a) A buck -boost regulator has an input voltage of V =15 V. The duty cycle δ = 0.30 and the switching frequency is 30 kHz. The inductance L= 150mH and filter capacitance F=220mF. The average load current Io = 1.5 A. Determine.
(i) the average output voltage, Vo;
(ii) the peak -to -peak output voltage ripple, ∆Vc; [8]
(b) Explain working principle of type - D Chopper along with circuit diagram and waveforms. [8]
OR
Q.5. (a) Describe the principle of step Up/ Down chopper. Derive an expression for the average output voltage in terms of input dc voltage and duty cycle. [8]
(b) Explain current commutated chopper along with circuit diagram and waveforms. [8]
| Earning: ₹ 6.90/- |
