Electrical Insulation Classes

Published on Jul 12, 2022 by Skipper

Insulating Material

A material that restricts free flow of electrical energy is known as an electrical insulator. These insulating materials are categorised into a number of classes based on their ability to endure a certain temperature. These ratings are important to consider when these insulating materials are used in electrical equipments like motors and transformers.

Classes of Insulation

Insulation Class	Maximum temperature (° C, Celsius)	Maximum temperature (° F, Fahrenheit)	Maximum temperature (K, Kelvin)
Y	90	194	363.15
A	105	221	378.15
E	120	248	393.15
B	130	266	403.15
F	155	311	428.15
H	180	356	453.15
C	180+	356+	453.15+

Examples materials of classes of insulations

Class Y (90 °C) - Silk, cotton, certain thermoplastics that soften above 90 °C

Class A (105 °C) - Reinforced silk, cotton and paper (with impregnated varnish or insulation oil)

Class E (120 °C) - Powder plastics, Polyurethane, molded polyvinyl epoxy resins, polyethylene terephthalat

Class B (130 °C) - Inorganic material such as Asbestos, Glass Fibres, Mica with varnish

Class F (155 °C) - Mica, class B materials that perform well at higher temperatures

Class H (180 C) - Fibre glass, mica, asbestos impregrenated in silicon rubber

Class C (180 C+) - Polyimide films, quartz, mica, teflon, polyimide enamel

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