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what is self healing capacitor
The system self-healing dielectric (self healing) in the event of failure of insulation metal layer is evaporated and the formation of an insulating layer, which is a very small impact on the performance of the capacitor is not. Many data sheets for metallized film capacitors refer to "self healing". This is an important feature for some applications. As shown in the drawing below, if the dielectric breaks down and forms a channel between the electrodes, a short circuit will be formed. However because of the very thin metallization (80 A to 300 A) of the electrodes, the current will typically be sufficient to melt back the metal from the shorted area and open the circuit. This is the principle of self healing.
Gas pressure created by metal vapor out of the area failed drives and thus an isolated area non-conductive and non-metalized layer is created in this location. And this time the condenser is running normally and no significant current is drawn from the grid. This characteristic will provide extra protection against high voltage transients across the device. To enhance this action some new designs have divided the metal into segments where the shorting current will fuse open the bad segment.
The disadvantages of self-healing capacitors
There are problems associated with self healing. the healing will leave residues of free carbon which can create excessive leakage. Second as the metal area is reduced with each healing the capacitor value will decrease and can cause a circuit failure.
The chart below is one example of a change of value after a series of healing cycles.
symbol of self healing capacitor
Capacitors with self-healing properties are the following symbol
advantage of self healing capacitor
The benefits of self-healing capacitors 1- lower weight and volume compared to the older generation capacitors.2- Because of the simple construction and low consumption, it is economical. 3- The low dielectric loss and capacitance reduces the heat generated and thus more capacitor life.