Analysis of major failures of metallized film capacitors

Metallized film capacitors are one of the capacitors commonly used in our lives. Metalized film capacitors have self-healing properties. So, how can it cause the failure of film capacitors?

1. Caused by partial discharge

Due to the existence of tiny air gaps in the medium during processing, air gaps caused by "over-healing" of metallized capacitors cause partial discharges of metallized film capacitors under the action of high voltages, and a large amount of heat can be quickly released inside the capacitors, which in turn causes The further destruction of the surrounding 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, but due to the dielectric loss and the presence of metal resistance and contact resistance inside the capacitor, the capacitor presents obvious configuration characteristics. When a load is applied, the metallized film capacitor heats up, and dissipates heat to the surrounding environment through the capacitor's surface. A temperature gradient is established from the middle to the surface. When the amount of heat is small, the heat dissipation balance; when the amount of heat is large, The heat radiation 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. For this reason, loss is the root cause of heat generation and the main factor causing failure of metallized film capacitors.

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