Part 1:
Q.1. Explain with diagrams, different types of rectifier circuits for producing high d.c. voltages.
Q.2. Why is a Cockcroft-Walton circuit preferred for voltage multiplier circuits? Explain clearly its operation when the circuit is (a) unloaded (b) loaded with a schematic diagram.
Q.3. Derive an expression for ripple voltage of a three-stage Cockcroft-Walton Circuit.
Q.4. Give an expression for ripple and regulation in voltage multiplier circuits. How are the ripple and regulation minimized?
Q.5. Define ripple voltage. Show that the ripple voltage in a rectifier circuit depends on the load current and the circuit parameters.
Q.6. Describe, with a neat sketch, the working of a Van de Graaff generator. What are the factors that limit the maximum voltage obtained?
Part 2:
1. Determine the ripple voltage and regulation of a 10 stage Cockcroft-Walton type d.c. voltage multiplier circuit having a stage capacitance = 0.01μF, supply voltage = 100kV at a frequency of 400Hz and a load current = 10mA.
2. A Cockcroft-Walton type voltage multiplier has 8 stages with capacitance, all equal to 0.05μF. The supply transformer secondary voltage is 125kV at a frequency of 150Hz. If the load current to be supplied is 5mA, find (a) the percentage ripple, (b) the regulation, and (c) the optimum number of stages for minimum regulation or voltage drop.
3. A two-stage Cockcroft-Walton voltage doubler is constructed from 0.05μF capacitors and a transformer with 100kV, 50Hz output. The output voltage is measured by an ammeter in series with a 100MΩ resistor, connected across the output terminals. Find the output terminal voltage and the peak-to-peak ripple for the following external load conditions:
(a) No connected load.
(b) 30 MΩ load.
(c) 3 MΩ load.
4. A voltage doubler circuit has C1 = C2 = 0.01μF and is supplied from a voltage source of V = (100sin314t) kV. If the d.c. output current is to be 4mA, Calculate the output voltage and the ripple.
5. A ten stage Cockcroft-Walton circuit has all capacitors of 0.06μF. The secondary voltage of the supply transformer is 100kV at a frequency of 150Hz. If the load current is 1mA, determine (a) the voltage regulation (b) the ripple (c) the optimum number of stages for maximum output voltage (d) the maximum output voltage.