Analysis of major failures of metallized film capacitors

Metallized film capacitors are one of the capacitors commonly used in life. Metallized film capacitors have the superior performance of self-healing. So, what causes the failure of metallized film capacitors?

Partial discharge

Due to the existence of tiny air gaps in the medium during processing, air gaps caused by "over-healing" of metallized film capacitors cause partial discharges of metallized film capacitors under high voltage. The capacitors will quickly generate a large amount of heat, which is too late to radiate and cause surroundings. The further destruction of the medium, the partial discharge intensified, and a vicious cycle was formed.

2. Temperature rise of capacitor caused by loss

An ideal capacitor has no amount of dissipation during operation. However, due to the dielectric loss and the presence of metal resistance and contact resistance inside the capacitor, the capacitor exhibits obvious configuration characteristics. Causes metallized film capacitors to generate heat when under load, and dissipates heat to the surrounding environment through the appearance of the capacitor. A temperature gradient is established from the middle to the appearance. When the amount of heat is small, the heat dissipation balance is generated; The heat dissipation cannot be balanced, the temperature of the capacitor rises, causing failure, causing the shell to expand, deform, crack, and melt the film into agglomerates. Burning will be found in severe cases.

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