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[ Iva ] What is a freewheeling diode, and what is its purpose?
[4 marks]
[ l-b] A diode circuit with an RL load is shown in fig.
with R=10 n, L=5 mH, and Vs=220 V
The switch SW is closed at t=O for a
period of 30 msec, and is then opened.
* determine an expression for the load current.
* find the value of load current when the switch is opened.
* sketch the load current waveform.
[8 marks]
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I Discuss the power factor improvement techniques?
[5 marks
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[ 2-b] A single-phase Thyristor half wave converter with resistive
load R=10 n, is supplied from 120 V (rms), 60 Hz.
If the average output voltage is 25% of the maximum average output voltage.
* derive an expression for both the average output voltage and rms output voltage.
* calculate the delay angle, the rms output current and the input power factor.
[ 8 marks
I
[ 3-a ] Write short notes on:
* Snubber circuit.
* Switching mode regulator.
* Classifications of dc chopper.
* thyristor commutation techniques.
* performance parameters of a rectifier.
[ 10 marks]
[ 2-a
[ 3-b] A single-phase ac voltage bidirectional controller has a resistive
[ 8 marks
load ofR=10 0, and the input voltage Vs =220 V(rms) at 50Hz.
The delay angle of the thyristors is n= 30° .
* Derive an expression for both the average output voltage and rms output voltage.
* Calculate the average output voltage, the rms output current, and the input power factor.
[ 4-a ] What are the differences between?
* Diode and Thyristor.
* GTO and TRIAC.
* Rectifier and Converter.
* On-Off and Phase Controllers.
* Step down and Step up dc chopper.
I
[ 10 marks]
[ 4-b ] A step-down chopper with a purely resistive load of R=10 n
[ 7 marks]
and the input voltage is 220 V . When the chopper switch
remains on , its voltage drop is 2 V and the chopping frequency is 1KHz. If the duty cycle is 70%
* Derive an expression for both the average output voltage and rms output voltage.
* Determine both the average and rms output voltage, also find the chopper efficiency.