Insulating materials are non-conductive materials under the allowable voltage, but not absolutely non-conductive materials. Under the action of a certain applied electric field strength, processes such as conduction, polarization, loss, and breakdown will also occur, and long-term use will also occur. .
The resistivity of insulating materials is very high, usually in the range of 1010 to 1022 Ω·m. As in a motor, the insulating material around the conductors isolates the turns and from the grounded stator core to ensure the safe operation of the motor.
Insulating materials are the foundation and guarantee for the development of electrical products, and play a particularly important role in the development of electrical machinery and electrical industries. The development and progress of insulating materials depends on the development of polymer materials and directly restricts and affects the development and progress of electrical products. .
Insulation material is the key to the advanced technology of electrical products, and it is also an important guarantee for the long-term safe and reliable operation of electrical products. Therefore, it is required to continuously develop new varieties of insulating materials and improve product performance and quality to meet the needs of the continuous development of electrical products.
There are many types of insulating materials, which can be divided into three categories: gas, liquid and solid. Commonly used gas insulating materials include air, nitrogen, and sulfur hexafluoride insulating PC films.
Liquid insulating materials mainly include mineral insulating oil and synthetic insulating oil (silicone oil, dodecylbenzene, polyisobutylene, isopropyl biphenyl, diarylethane, etc.).
Solid insulating materials can be divided into two categories: organic and inorganic. Organic solid insulating materials include insulating paint, insulating glue, insulating paper, insulating fiber products, plastics, rubber, varnished varnished pipes and insulating impregnated fiber products, electrical films, composite products and adhesive tapes, electrical laminates, etc. Inorganic solid insulating materials mainly include mica, glass, ceramics and their products. In contrast, solid insulating materials are diverse and most important.
Different electrical equipment has different requirements for the performance of insulating materials. Insulation materials for high-voltage electrical installations such as high-voltage motors and high-voltage cables require high breakdown strength and low dielectric loss. Low-voltage electrical appliances take mechanical strength, elongation at break, heat resistance grade, etc. as the main requirements.
The macroscopic properties of insulating materials such as electrical properties, thermal properties, mechanical properties, chemical resistance, weather resistance, corrosion resistance and other properties are closely related to its chemical composition and molecular structure. Inorganic solid insulating materials are mainly composed of silicon, boron and various metal oxides, mainly ionic structure, the main feature is high heat resistance, working temperature is generally greater than 180 ℃, good stability, resistance to atmospheric aging, resistance Good chemical properties and long-term aging performance under the action of an electric field; but high brittleness, low impact strength, high pressure resistance and low tensile strength; poor craftsmanship. Organic materials are generally polymers with an average molecular weight between 104 and 106, and their heat resistance is usually lower than that of inorganic materials. The heat resistance of materials containing aromatic rings, heterocyclic rings and elements such as silicon, titanium, and fluorine is higher than that of general linear polymer materials.
The important factors affecting the dielectric properties of insulating materials are the strength of molecular polarity and the content of polar components. The dielectric constant and dielectric loss of polar materials are higher than those of non-polar materials, and it is easy to adsorb impurity ions to increase conductivity and reduce its dielectric properties. Therefore, attention should be paid to cleanliness during the manufacturing process of insulating materials to prevent pollution. Dielectrics for capacitors require high dielectric constants to improve their specific characteristics.