INTRINSIC OR IONIC BREAKDOWN MECHANISM OF SOLID DIELECTRICS|BREAKDOWN IN SOLIDS|HIGH VOLTAGE ENGINEERING
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The document discusses intrinsic (ionic) breakdown in high voltage engineering, specifically in solid dielectrics under short-duration voltage applications. It explains the phenomenon's dependence on free electrons and details types of breakdown including electronic and avalanche breakdowns. The maximum electrical strength recorded is noted, with specific conditions leading to breakdown outlined.
INTRINSIC OR IONIC BREAKDOWN MECHANISM OF SOLID DIELECTRICS|BREAKDOWN IN SOLIDS|HIGH VOLTAGE ENGINEERING
- 1. HIGH VOLTAGE ENGINEERING INTRINSIC (IONIC) BREAKDOWN IN SIMPLE LAUNGUAGE LEC # 17 BREAKDOWN IN SOLIDS
- 2. 2Prof. Prasant Kumar High Voltage Engineering INTRINSIC BREAKDOWN OR IONIC BREAKDOWN When voltages are applied only for short durations of the order of 10-8 sec the dielectric strength of a solid dielectric increases very rapidly to an upper limit called the intrinsic electric strength. The maximum electrical strength recorded is 15 MV/cm for poly vinyl alcohol at - 196˚C. Intrinsic breakdown depends upon the presence of free electrons which are capable of migration through the lattice of the dielectric.
- 3. 3Prof. Prasant Kumar High Voltage Engineering Types of Intrinsic Breakdown: INTRINSIC BREAKDOWN OR IONIC BREAKDOWN Avalanche or Streamer Breakdown Electronic Breakdown
- 4. 4Prof. Prasant Kumar High Voltage Engineering Electronic Breakdown Intrinsic breakdown occurs in time of the order of 10-8 sec and therefore is assumed to be electronic in nature. When an electric field is applied, electrons gain energy from the electric field and cross the forbidden energy gap from the valence to the conduction band. When this process proceeds continuously, more and more electrons get collected in conduction band, and it leads breakdown. INTRINSIC BREAKDOWN OR IONIC BREAKDOWN
- 5. 5Prof. Prasant Kumar High Voltage Engineering Avalanche or Streamer Breakdown This is similar to breakdown in gases due to cumulative ionization. Conduction electrons gain sufficient energy above a certain critical electric field and cause liberation of electrons from the lattice atoms by collisions. Under uniform field conditions, if the electrodes are embedded in the specimen, breakdown will occur when an electron avalanche bridges the electrode gap. INTRINSIC BREAKDOWN OR IONIC BREAKDOWN
- 6. 6Prof. Prasant Kumar High Voltage Engineering