The insulating plate is usually a thin sheet material formed by depositing the fibers on the paper machine through water or other media, which is composed of plant fibers, mineral fibers, synthetic fibers or their mixtures. With high tear resistance, low elongation and good insulation, insulating paper is widely used as insulating material in motors, cables, capacitors and transformers, and is also the main component of insulating materials such as laminated products, composite materials and prepreg materials.
Due to the special use of insulating paper, it is required that it must have some characteristics different from other types of paper, mainly including mechanical properties, electrical properties and thermal stability.
1. Mechanical properties
During use, the insulating paper will be affected by various external forces. For example, the insulating paper used for high-voltage large capacity generators must be able to withstand the large mechanical stress caused by high-speed rotation, starting and stopping, and sudden short circuit. Therefore, it is required to have high mechanical properties, mainly including tensile strength and elongation at break.
2. Thermal stability
Thermal stability is a very important indicator of insulating paper, and is a major factor that causes low-voltage insulation aging, which determines its service life. Under normal operation, the electric field strength has only a slight impact on the insulation aging process. If insulating paper is used in a high temperature environment for a long time, it will become brittle due to thermal aging and gradually lose its mechanical and electrical properties.
3. Electrical performance
Insulating sheet is widely used in electrical equipment, so it needs to meet certain electrical performance. The electrical properties of insulating paper refer to its polarization, conductivity, dielectric loss and breakdown characteristics under the action of electric field.
The properties of insulating plates are interrelated and cannot be viewed separately. In the process of selecting and developing materials, it is necessary to comprehensively balance the advantages and disadvantages of various materials. In addition, to produce insulating paper with good electrical performance, impurities such as metal ions, bubbles and moisture should be avoided as much as possible during the production process, and the insulating paper should have a high uniformity.
