Film Technology To Replace Electrolytic Technology

Film Technology To Replace Electrolytic Technology
Written By: Gilles Terzulli | Billy W. Peace

Abstract:
Since 1980, great improvements have been made on DC filter capacitors using a combination of metallized plastic films and different segmentations of the metallization on those film dielectrics. Volume and weight have been reduced by a factor of 3 or 4 over the last years. Now film manufacturers have developed thinner films and have improved segmentation techniques used on the metallization which has helped immensely in the improvement of such capacitors. Using non-gas impregnated designs, the voltage ranges between 600 VDC and 1200 VDC can be more economically covered by film capacitors rather than electrolytic. Depending on the application, over 1200 VDC, vegetable oil-filled versions are recommended.

Consequently, the trend of industrial and traction market for power conversion is to replace electrolytic capacitors with film technology. This trend is generated by many advantages that film technology offers.

These include:
• High rms current capabilities up to 1ARMS per µF
• Over voltage withstanding up to 2 times the rated voltage
• Handle voltage reversal
• High peak current capabilities
• No acid inside
• Long lifetime
• No storage problem

However, this replacement won’t be done “microfarad for microfarad”, but for the total function. Indeed, despite the very big improvement of film technology, replacement solution won’t be possible for each application. In order to help the user understand, we will present some concrete figures where film gives major benefits over electrolytic technology.

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