STUPIDSID
1 (a)
Give symbol, characteristics features of the following devices:
GTO, TRIAC, MOSFET, UJT, SCR.
GTO, TRIAC, MOSFET, UJT, SCR.
10 M
1 (b)
Explain briefly the different types of thyristor power converters and mention two applications of each.
10 M
2 (a)
With the necessary waveforms, explain the switching characteristics of a power transistor.
8 M
2 (b)
Give the comparison between MOSFET and IGBT.
6 M
2 (c)
The collector clamping circuit of Fig. Q2 (c) has VCC=100 V, RC=1.5 Ω. Vd1=2.1 V, Vd2=0.9 V, VBE=0.7 V, VB=15 V and RB=2.5 Ω and β=16. Calculate
i) the collector current without clamping.
ii) the collector-emitter clamping voltage VCE.
iii) the collector current with clamping.
i) the collector current without clamping.
ii) the collector-emitter clamping voltage VCE.
iii) the collector current with clamping.
6 M
3 (a)
Define the following: i) latching current ii) holding current iii) I2t rating. Derive expression for Anode current using two-transistor model in case of SCR.
10 M
3 (b)
What is the need for protection of thyristor? Explain how thyristors are protected against high \( \dfrac {di}{dt} \text{ and high } \dfrac {dv}{dt}. \)
6 M
3 (c)
A SCR has a \( \dfrac {di}{dt} = 120 \text{A /}\mu\text{ s and a} \dfrac {dv}{dt} \) of 300 V/μs it operates on a 250 V DC source with a load resistance of 10 Ω. Find the suitable values for the components of the snubber circuit.
4 M
4 (a)
Explain the working of single phase dual converter with neat circuit diagram. Draw relevant waveforms.
10 M
4 (b)
Explain the working of single phase semiconvert with neat circuit and waveforms. Derive expression for the average output voltage.
6 M
4 (c)
A single phase full converter supplies an RLE load form a 230 V, 50 Hz supply. The load is highly inductive, so that load current is continuous and ripple free. If R=1 Ω and the load current is IO=10A. Calculate the delay angle α for E=120.
4 M
5 (a)
Explain the operation of single phase bidirectional controller with resistive load. Obtain the expression for RMS output voltage. Show the waveforms.
10 M
5 (b)
A single phase full wave AC voltage controller has an RL load. The input voltage is 230 V, 50 Hz and the load is R=2 Ω and XL= 2Ω α1= α2= π/2. Calculate the following:
i) Angle until which the thyristor conducts.
ii) Conduction angle of thyristor.
iii) RMS voltage of output.
i) Angle until which the thyristor conducts.
ii) Conduction angle of thyristor.
iii) RMS voltage of output.
6 M
5 (c)
What are the advantages and disadvantages of ON-OFF control and phase control of ac voltage controller?
4 M
6 (a)
Explain the resonant pulse communication with neat circuit and waveforms.
10 M
6 (b)
Explain the working of complementary communication circuit. Draw relevant waveforms. Derive expression for toff.
6 M
6 (c)
In the circuit of Fig. Q6 (c) the capacitor is initially charged to a voltage of VC(0)=500 V. If L=15 μH and C=50 μF and the SCR is turned ON at t=0. Calculate
i) the peak value of resonant current and (ii) the conduction time of thyristor.
i) the peak value of resonant current and (ii) the conduction time of thyristor.
4 M
7 (a)
Give the classification of chopper. Explain briefly each one of them.
10 M
7 (b)
Explain the principle of operation of a step up chopper.
6 M
7 (c)
A DC chopper has an input voltage of 200 V and a load of 8 Ω resistance. The voltage drop across thyristor is 2 V and the chopper frequency is 800 Hz. The duty cycle K=0.4. Find
i) Average output voltage
ii) RMS output voltage
iii) Chopper efficiency.
i) Average output voltage
ii) RMS output voltage
iii) Chopper efficiency.
4 M
8 (a)
Explain the performance parameters of inverters.
6 M
8 (b)
Explain the working of transistorized current source inverter.
8 M
8 (c)
Calculate the RMS values of the fundamental and the two lower order harmonics of a single-phase full bridge inverter employing single-pulse width modulation for output voltage control. The modulation index is 80% and the dc input voltage is 230 V.
6 M
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