The Sealed Tube Chemical Compatibility Test (CCT) is a short-time test procedure to determine if the new materials to be added to the established EIS will cause detrimental degradation of the EIS.
Simply put, the all of the materials in the established EIS, including twisted pairs of the original MW coated with the original varnish, are sealed in a glass tube designated as the Control EIS. In a second tube are sealed all of the materials in the established EIS along with the desired additional components for evaluation as the Candidate EIS. The Candidate EIS tube will also include twisted pairs of either the original MW coated with the original varnish or the original MW coated with a suitable substitute varnish.
The Control and Candidate tubes are then aged for two weeks at the established EIS temperature rating plus 25°C; for example, a Class 180(H) EIS will be thermally aged at 205°C. The tubes are allowed to cool and then the varnish-coated MW samples are subjected to dielectric strength testing to determine if the addition of the new components in the candidate tube have caused degradation greater than 50% over those in the control tube. If not, the Candidate EIS is now acceptable as a UL Recognized EIS.
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