Most of the customers who buy power capacitors in the industry now choose dry capacitors. The reason for such a situation is inseparable from the advantages of dry capacitors themselves. Compared with oil capacitors, they have many advantages in terms of product performance, environmental protection and safety. Dry capacitors have now gradually become the mainstream of the market. Why is it recommended to use dry capacitors? Come to this week’s article to learn more about it. 

Self-healing capacitors are divided into two types of construction: oil capacitors and dry capacitors. Dry capacitors, as the name implies its chosen filler is a non-liquid type of insulation. The fillers for dry capacitors in the industry today are mainly inert gases (e.g. sulfur hexafluoride, nitrogen), microcrystalline paraffin and epoxy resin. The majority of oil-immersed capacitors use vegetable oil as the impregnating agent. Dry capacitors don’t apply environmentally harmful chemicals such as impregnants and paints in the production process. Considering the raw materials, production process, energy consumption, performance in life cycle and transportation and final disposal, all the environmental impact evaluation indexes are due to oil capacitors, which can be called an environmentally friendly capacitor product.

There are different types of power capacitors in the market now, but very few companies use oil capacitors. There are two main reasons for the abandonment of oil capacitors.

1. Safety aspects

When oil capacitors are in operation, on the one hand, oil seepage and leakage will lead to the breakdown of internal components; on the other hand, the shell will lead to oil seepage and leakage of capacitors due to corrosion.

1. Insulation aging will cause the capacity of capacitors to drop

The insulation oil of oil capacitor will increase the acid value as the aging degree increases, and the acid value increases faster as the temperature rises; the insulating oil of oil capacitor also generates acid and water in the aging, and the water has a corrosive effect on the metalized film, which leads to the capacity of power capacitor decreasing and the loss increasing. Whether it’s a capacitor capacity drop or a safety hazard problem, most problems are caused by insulating oil. If gas is used as the filling medium, it can not only prevent the capacitor capacity from decreasing due to aging, but also solve the problem of oil seepage and oil leakage.

Besides, the safety performance of dry capacitors and oil capacitors are different,

Oil capacitor: It is characterized by good heat dissipation and good insulation performance. However, because of the insulating oil component inside, when it meets open flame, it may help to ignite and cause fire. Moreover, when oil capacitors are transported or have other conditions, it will cause damage to the capacitor and the oil seepage and leakage mentioned earlier in the article will occur.

Dry capacitor: It has poor heat dissipation performance and require high thickness of polypropylene metallization film. However, because the internal filling is insert gas or epoxy resin, it can inhibit combustion when there’s an open flame. Moreover, dry capacitors do not suffer from oil seepage or leakage. Compared with oil capacitors, dry capacitors will be safer.

In terms of transportation, compared with oil capacitors, dry capacitors are lighter in mass with internal filling gas and epoxy resin, so transportation, handling and installation are lighter, which can reduce the difficulty of installation and maintenance to a certain extent and facilitate the use.

In addition, with the continuous development of capacitor manufacturing technology and product applications, the application of dry structure will become more and more extensive and will gradually replace the oil structure. Oil-free dry capacitor is the future development trend.