TC6.3-3E5 データシート - Ferroxcube International Holding B.V.

Coating
   The cores are coated with parylene C, flame retardant in
   accordance with “UL 94V-2”; UL file number E 194397.
   The coating is transparent.
   Maximum operating temperature is 90 °C.

Isolation voltage
   DC isolation voltage: 1000 V.
   Contacts are applied on the edge of the ring core, which is
   also the critical point for the winding operation.