break down in solid dielectric
BREAKDOWN IN SOLID DIELECTRIC
The needs of good dielectric:
Low dielectric reduction,
Excessive mechanical power,
Clear of gaseous inclusions, and dampness,
Immune to thermal and chemical destruction.
Solid dielectrics have larger breakdown power compared to liquids and gas. When break down occurs, shades get permanently damaged while gases completely and liquids partly restore their di-electric strength. Break down mechanism may differ depending on the moments of application of ac electricity as displayed in Physique 1 and can be classified as follows:
Optimum strength generally obtainable ranges from 5 - twelve MV/cm.
Intrinsic malfunction depends upon the presence of free electron which in a position of migration through the essudato of the dielectric. Usually tiny numbers of leasing electrons exist, with some structural imperfections and small amounts of impurities. The impurity atoms or substances act as traps for the conduction electrons up to certain ranges of electric fields and temperatures. When these ranges are surpass, additional electrons and caught are released and participate in the louage process.
Two types of intrinsic breakdown mechanisms:
Assumed to be electric in mother nature (occurs over time 10-8 s)
Preliminary density of conduction (free) electrons presumed to be significant and electron-electron collisions arises.
Once electric discipline is applied, electrons gain energy and cross the forbidden difference from the valency to the conduction band. This procedure repeated, a growing number of electrons found in
conduction band, eventually resulting in breakdown.
a. Intrinsic or perhaps ionic breakdown
b. Electromechanical breakdown
c. Thermal break down
d. Electrochemical breakdown
at the. Treeing and tracking
When ac electricity is used only for brief durations with the order 10-8Sec, the di-electric strength of a solid di-electric increases extremely rapidly to an upper...
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