An insulation class is the maximum continuous temperature an electrical insulation system is rated for. IEC 60085 defines the classes by temperature: Class B is 130 °C, Class F 155 °C and Class H 180 °C. Polyester films are typically Class B, aramid-polyester laminates Class F, and aramid papers Class H.
| Thermal class (°C) | Letter designation |
|---|---|
| 90 | Y |
| 105 | A |
| 120 | E |
| 130 | B |
| 155 | F |
| 180 | H |
| 200 | N |
| 220 | R |
| 250 | — |
The number is the class; the letter is the older designation still printed on most datasheets and nameplates.
| Material | Class | Temperature |
|---|---|---|
| Mylar and PET polyester film | B | 130 °C |
| FR4 and G10 epoxy-glass sheet | B | 130 °C |
| Gar-Flex APA (aramid-polyester-aramid) | F | 155 °C |
| Nomex (aramid) paper | H | 180 °C |
| G11 epoxy-glass sheet | H | 180 °C |
The class applies to the insulation system as rated: the temperature at which it is expected to deliver its rated service life. It is a thermal rating, separate from the dielectric strength of the material, which is quoted in kV/mm.
180 °C, under IEC 60085.
155 °C, under IEC 60085.
130 °C, under IEC 60085.
Nomex (aramid) paper and G11 epoxy-glass sheet.
Perfect Insulations has manufactured thermal and electrical insulation in Bengaluru since 1995 and works to ISO 9001:2015. Send your drawing or specification with the material, thickness and quantity.