Our RnD engineers have been busy with some interesting tests. This white paper summarises the test results from a comparison of Tervakoski Film ECT and EC film. Additionally, we have also benchmarked Tervakoski Film ECT and an experimental tenter film (EXC) made in TGF from an alternative common high isotatic polymer.
A bit of background
The required lifetime for smart grid capacitors is decades – 30, even 40 years nowadays – much longer than in classic metallised film capacitors. In other words, electrical ageing (local or general) of the capacitor film is a risk factor from the capacitor’s lifetime point of view. The film’s dissipation factor and its change as a function of temperature and time are very critical.
In recent years, the market has been moving continuously towards high crystalline films (HIPP). In some segments, e.g. DC applications, HIPP films are used almost exclusively. However, our long-term tests have shown that there are certain weaknesses in commonly available HIPP films, regarding AC ageing and ripple current conditions – especially at higher temperatures. The same things have been observed for the experimental film ECX, used for benchmarking in this white paper.
What we did
We wanted to generate a “real” High Temperature/High Endurance Capacitor Film without compromising the positive features of our EC base film. On the other hand, there was also a need to improve our “normal crystallinity” base film EC, to withstand higher temperatures mechanically and from an endurance point of view. For example, smart grid and automotive applications require a superior film for high demanding metallised AC DC and AC film capacitors.
OUR TESTS:
• DC breakdown strength – routine test results comparison
• Accelerated AC voltage endurance tests at elevated temperatures
• Long term ageing test
What we found
Results clearly show an overall superiority of Tervakoski Film ECT film vs. EC regarding breakdown strength characteristics. The ECT film also displays exceptional safety regarding local ageing. The new high-temperature film performs clearly better than a classic base film (“low dissipation factor film“). At room temperature, both film types had approximately the same initial dissipation factor. The characteristic is important in AC applications but also in DC capacitors due to the existence of ripple current.