Switch to Nomex-Insulated Conductor in Dry-Type Transformer Production

With rising demand for projects requiring indoor installation, the customer decided to expand its dry-type transformer series. Because of the higher winding temperatures that come with air cooling, the existing cellulosic insulation solution was not sufficient; a switch to conductor insulated with aramid-based paper came onto the agenda.

During the transition, the number of insulation layers, overlap ratio and total insulation thickness were evaluated together with the winding geometry. Aramid paper requirements were defined with reference to IEC 60819; the thermal-class declaration was compared with the manufacturer test reports and compatibility with the other system components (cast resin, slot insulation) was checked.

A short trial batch was first produced for sample winding; after tension and overlap settings were verified on the winding line, series supply began. The aramid-insulated batches, though low in moisture sensitivity, were shipped in sealed packaging.