Passive Components


Plastic film capacitors reliable and stable

28 August 2002 Passive Components

Eurofarad designs and manufactures film capacitors for professional applications. A wide range of technologies is used depending on environmental considerations. In general, Eurofarad impregnates the capacitors with solid thermoset resin such as epoxy, polyester or composites. These technologies result in extremely stable mechanical and electrical properties at temperatures ranging from -55 to +125°C/+155°C and even up to +200°C if required.

The company's high voltage capacitors are especially recommended because their performance offers optimum results for energy storage, delay lines or low impedance circuits. For these applications, life expectancy depends on several different factors: form and mode of discharge, frequency of recurrence, mode of operation, climatic condition, etc.

The use of plastic film as a dielectric has the following advantages: high electrical and climatic performance; homogenous; consistant repeatability; and very thin film which allows smaller size components to be used.

The metallised dielectric technique replaces the metal foil of the armatures of traditional capacitors with a very thin coating of metal on the dielectric film. This is deposited at high vacuum. It allows further reduction in size.

Breakdown due to ageing or dielectric overstrain is permanent in traditional foil armature capacitors. In metallised dielectric capacitors this is a short term phenomenon - as the current of the short circuit evaporates the metallisation at the defective spot and the capacitor is again insulated - hence 'self-healing' effect.

Several metals can be used for metallisation of the film. Eurofarad only uses aluminium as, firstly, it is a very good conductive material which favours a low loss angle; and secondly, the residue of self-healing is alumina, which is a very good insulating substance and consequently nonpolluting within the capacitor.

* Foil armature capacitors: For particular cases where these are necessary (very small capacitors, high current, etc) the company makes traditional foil armature capacitors.

* Composite dielectric capacitors: The use of two different dielectrics in the same capacitor sometimes proves interesting and allows the advantages of two dielectrics. For example in the case of metallised composite capacitors this technique makes impregnation easier, avoids ionisation and gives excellent long term stability in all environmental conditions.

* Other capacitors: Eurofarad also offers capacitors with made to order characteristics such as: partial discharge-free capacitors; specific test voltage capacitors; and capacitors to individual technical specifications.



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