1、Classification of insulating materials
Electrician commonly used insulating materials according to chemical properties that can be divided into inorganic with materials, organic insulating materials and mixed insulating materials.
(1) inorganic insulating materials: there are mica, asbestos, marble, porcelain, glass, sulphur, etc., mainly do motor, electrical winding insulation, switch base plate and insulators, etc.
(2) organic insulating materials: there are insect glue, resin, rubber, cotton yarn, paper, hemp, silk, rayon, mostly used in the manufacture of insulating paint, winding wire covered with insulation, etc.
(3) mixed insulating materials: a variety of molding insulating materials made from the above two materials used as the base of electrical appliances, shells, etc.
2、Performance indicators of insulating materials
Performance indicators of insulating materials commonly used in electrical engineering like insulation strength, tensile strength, specific gravity.
(1) Compressive strength: insulating material in the electric field, when the electric field strength increases to a certain limitation, it will break down. This insulation breakdown of the electric field strength is called insulation withstand voltage strength (also known as dielectric strength or insulation strength) which usually mark with 1mm thick insulation material can withstand the voltage KV value .
(2) tensile strength: insulation material per unit cross-sectional area can withstand the tensile force. For example, glass per square centimetre cross-sectional area can withstand 140 kg.
(3) Density: the mass of the insulating material per cubic metre of volume. For example, sulphur has 2 grams per cubic metre of volume.
(4) Expansion coefficient: the degree of volume increase after the insulator has been heated.
3、Heat-resistant grade of insulating material
(1) Y-class insulating materials: natural textiles such as wood, cotton and fibre, textiles based on acetate and polyamide, and solvents with easy decomposition and low melting points. Ultimate working temperature: 90 degrees.
(2) Class A insulating materials: Y-grade materials working in mineral oil and impregnated with oil or oleoresin compound glue, enamelled wire, enamelled cloth, enamelled silk insulation and oil-based lacquers. Bitumen enamels etc. Ultimate working temperature: 105 degrees.
(3) Class E insulating materials: Mylar film and Class A material laminated, glass cloth, oil-based resin lacquer, polyvinyl acetal high-strength enamelled wire, vinyl acetate heat-resistant enamelled wire. Ultimate working temperature: 120 degrees.
(4) Class B insulating materials: mylar film, mica impregnated with suitable resin bonding, glass fibre, asbestos, etc., mylar lacquer, mylar enamelled wire. Limit working temperature: 130°C.
(5) Class F insulating materials: mica products with organic fibre reinforcement, glass wool and asbestos, glass wool cloth, laminated products based on glass wool cloth and asbestos fibres with inorganic materials as reinforcement and mica powder products with inorganic materials as reinforcement and stone tape reinforcement, polyester or alkyd materials with good chemical thermal stability, composite silicone organic polyester lacquer. Extreme working temperature: 155 degrees.
(6) H-class insulation materials: mica products without reinforcement or inorganic materials as reinforcement, thickened F-class materials, composite mica, silicone mica products, silicone organic paint silicon organic rubber polyimide composite glass cloth, composite film, polyimide lacquer, etc. Ultimate working temperature: 180 degrees.
