The concept of capacitance breakdown
Capacitance of the dielectric to withstand the electric field strength is a certain limit, when the bound charge out of the atomic or molecular binding and participate in the conductive, it destroys the insulating properties, this phenomenon is known as the dielectric breakdown.
Capacitor breakdown conditions
Capacitor breakdown conditions to reach the breakdown voltage.
Breakdown voltage is the limit voltage of the capacitor, more than this voltage, the capacitor medium will be broken. Rated voltage is the capacitor can withstand long-term work voltage, it is lower than the breakdown voltage. Capacitors in not higher than the breakdown voltage are safe and reliable work, do not mistakenly think that the capacitor is only in the rated voltage work is normal.
Definition of PN junction critical breakdown voltage corresponding to the PN junction breakdown voltage BV, BV is an important parameter to measure the reliability of the PN junction and the use of an important parameter in the PN junction of the other performance parameters remain unchanged, the higher the value of BV the better.
Capacitor breakdown is open circuit or short circuit
Capacitor breakdown is equivalent to a short circuit, the reason is that when the capacitor is connected to the DC is to look at the open circuit, connected to the AC power to look at the short circuit, capacitance has a nature is through the cross-separation of straight, the term breakdown in the understanding of the electrician is a short circuit, the formation of the breakdown of the main reason is that the outside world voltage exceeds the nominal voltage resulting in permanent damage, called breakdown.
When a destructive discharge occurs in a solid dielectric, it is called a breakdown. Breakdown, leaving traces in the solid dielectric, so that the solid dielectric permanent loss of insulating properties. For example, when an insulating cardboard is punctured, a hole is left in the cardboard. It can be seen that the term breakdown is limited to solid dielectrics.
Causes of Capacitor Breakdown
The fundamental cause of capacitor breakdown is the destruction of the dielectric insulation, resulting in polarization. Some of the reasons for the destruction of dielectric insulation are:
The operating voltage exceeds the maximum withstand voltage of the capacitor;
Capacitor quality is not good, leakage current is large, the temperature gradually rises, the insulation strength decreases.
Methods to avoid dielectric breakdown
Use materials with high dielectric strength;
Insulating materials have a certain thickness and do not contain impurities such as air bubbles or moisture;
Trying to make the electric field distributed as required to avoid power lines being too dense in certain places.
The polarity of the capacitor is reversed or connected to the AC power supply.
Can capacitors be restored after breakdown?
If the dielectric is a gas or a liquid, it is a self-recovering insulating medium and the breakdown is reversible;
The dielectric is solid, the breakdown is irreversible, is the only breakdown of the insulation medium can not be recovered.
