High voltage
(a) Consider a spherical globule diameter of 1 µm of liquid permittivity of 4 immersed in a liquid dielectric of permittivity 2, which is shown in Figure. When it is subjected to an electric field between parallel electrodes, the electrostatic forces cause the globule to elongate and take the shape of a spheroid and the diameter of the spheroid decreases to 0.5 µm. Prove that the electric field inside the globule becomes 75% of the applied field between the electrodes i.e. E=0.75E0
Where, E is electric field between the electrodes with bubble and E0 is the field in the liquid in the absence of the globule.
(b) In the above arrangement for a droplet of water having diameter of 2 µm, permittivity of 90 in an insulating oil having permittivity of 2, if the globule keeps on elongating eventually causing bridging of the electrodes, and breakdown of the gap, calculate and tabulate the critical field in kV/cm with 0.25µm steps from the varying radius of water droplet from 0.5µm to 1µm and the surface tension of the globule of
.043 N/m. [7+3=10]
(2) (a) Draw the Lightning Impulse Voltage and Switching Impulse wave shape separately, mentioning the front time & tail time for each case separately with neat sketch.
(b) Find out the charging voltage of a 400 kV, 4 stages “Cockroft Walton Multiplier circuit” in smoothing capacitor output and draw the same with neat sketch mentioning the voltage in each stage with capacitors and diodes with proper component labels.
[5 +5=10]