How electrical insulating materials are classified by heat resistance

Electrical insulating materials for heat resistance (heat resistance) are divided into seven classes: Y, A, E, F, B, H, C. Each class is characterized by the maximum permissible temperature at which the long-term safety of the insulation is guaranteed.

Class Y includes materials from non-impregnated and non-immersed in liquid dielectric fibrous materials: cotton fibers, cellulose, cardboard, paper, natural silk and their combinations. The limiting temperature is 90 °C.

Up to class A includes class Y materials, as well as viscose materials impregnated with oil, oleoresin and other insulating varnishes. The limiting temperature is 105 °C.

Up to Class E includes certain synthetic organic films, fibers, resins, compounds and other materials. The limiting temperature is 120 °C.

Up to class B includes materials based on mica, asbestos and fiberglass, made using organic binders with conventional heat resistance: mical tape, asbestos paper, fiberglass, fiberglass, micanite and other materials and their combinations. The limiting temperature is 130 °C.

Up to class F includes materials based on mica, asbestos and fiberglass, impregnated with resins and varnishes with suitable heat resistance. The limiting temperature is 155 °C.

Class H includes mica, asbestos and fiberglass used with silicon binders and impregnating compounds. The limiting temperature is 180 °C.

Up to class C include mica, ceramics, glass, quartz or their combinations, used without binders and materials of organic origin. The working temperature of class C insulation is above 180 ° C. The temperature limit is not set.

Insulation grade Y in electrical engineering is almost never used, and insulation C is rarely used.

Insulating materials must also have thermal conductivity (to prevent overheating of live parts), mechanical strength and moisture resistance.

Read also: Characteristics of electrical insulating materials