As fire-resistant cables are now more and more widely used, many manufacturers are producing them, but often the quality cannot be guaranteed. Therefore, under normal circumstances, when companies develop fire-retardant cable products, they first try to manufacture a section of the product, send it to the relevant national inspection agency, and then start mass production after obtaining the test report. A few cable manufacturers have established their own fire-resistant test inspections. As everyone knows, the fire resistance test is an inspection of the process results of the cables produced. The same process plan and the performance of the cables produced in different periods have certain differences. For companies that produce fire-resistant cables, it is like the fire-resistant test of the fire-resistant cable. With a pass rate of 99%, the fire-resistant cable has a 1% safety hazard, which is 100% dangerous for users. So how to improve the pass rate of fire-resistant cable fire-resistant experiments, from the raw materials, conductor selection, production process control and other aspects to explain
1. There are three types of mica, synthetic mica, phlogopite, and muscovite. The quality performance of each is the best synthetic mica and the worst muscovite. For small-sized power cables, synthetic mica tape must be selected for wrapping, and mica tape cannot be layered. Use, long-term storage of mica tape is easy to absorb moisture, so the temperature and humidity of the surrounding environment must be considered when storing mica tape.
2. When selecting mica tape wrapping equipment, it should be used with good stability. The wrapping angle is best to wrap around 300-400. The mica tape is wrapped evenly and tightly. All guide wheels and rods that touch the equipment must be smooth. The wiring is neat, the tension is not too large, and the side plate and cylinder of the take-up tooling wheel are flat and smooth.
3. For the circular core with axial symmetry, the mica tape is wrapped tightly in all directions, so the conductor structure of the fire-resistant cable should adopt a circular compact conductor. The reasons are as follows:
①Some users propose that the conductor is a stranded flexible cable, which requires the company to communicate with users from the reliability of the cable to a round compact conductor. The soft structure of the bundle and the twisting can easily cause damage to the mica tape as a fire-resistant Cable conductors are not desirable, but some manufacturers think that users need what kind of fire-resistant cables, and manufacturers should meet user needs. I think users do not fully understand the details of cables after all. Cables are closely related to human life. Yes, cable manufacturers must clarify related technical issues to users.
②Sector-shaped conductors are not suitable, because the pressure of the mica tape of the fan-shaped conductor is unevenly distributed. As shown in the figure, it can be seen that the pressure at the three fan-shaped corners of the fan-shaped core around the mica tape is the largest Yes, because mica is a sheet-like silicate polymer, the molecular attraction between the layers is much weaker than the s1-0 covalent bond in the crystal. The layers are easy to slide and adhere to silicon, but the bonding strength is also Low, it is easy to fall off and split when external force is scraped and squeezed, especially when the fan-shaped structure is adopted, the wrapped wire core passes through the guide wheel, the wire splitting rod and the wire to the edge of the side plate of the tooling wheel, and the rear track When the process extrudes the insulation into the core, it is easy to be scratched and bumped, which leads to a decrease in electrical performance. In addition, from the perspective of cost, the section perimeter of the sector-shaped conductor structure is larger than the section perimeter of the circular conductor, which increases the precious material mica Belt, although the outer diameter of the circular structure cable has increased. The amount of polyvinyl chloride sheathing material has increased, but the product material is compared with the total cost, and the overall cost of the circular structure cable is still saved. Based on the above description, from the technical and economic analysis, it is best to use a circular structure for the conductor of the fire-resistant power cable.