Mica tape is a high-performance mica insulating product with excellent high temperature resistance and combustion resistance. Mica tape has good flexibility in normal state and is suitable for the main fire-resistant insulating layer in various fire-resistant cables. There is basically no volatilization of harmful fumes when burning in an open flame, so this product is not only effective but also safe when used in cables.
Mica tapes are divided into synthetic mica tape, phlogopite mica tape, and muscovite mica tape. The quality and performance of synthetic mica tape is the best and muscovite mica tape is the worst. For small-sized cables, synthetic mica tapes must be selected for wrapping. The mica tape cannot be used in layers, and the mica tape stored for a long time is easy to absorb moisture, so the temperature and humidity of the surrounding environment must be considered when storing the mica tape.
When using mica tape wrapping equipment for refractory cables, it should be used with good stability, and the wrapping angle should preferably be 30°-40°. All guide wheels and rods that are in contact with the equipment must be smooth, the cables are neatly arranged, and the tension is not easy to be too large. .
For the circular core with axial symmetry, the mica tapes are tightly wrapped in all directions, so the conductor structure of the refractory cable should use a circular compression conductor. The reasons for this are as follows:
① Some users propose that the conductor is a bundled soft structure conductor, which requires the company to communicate with users from the reliability of cable use to a circular compression conductor. The soft structure bundled wire and multiple twists can easily cause damage to the mica tape, which is used as a fire-resistant Cable conductors are not acceptable. Some manufacturers think that what kind of fire-resistant cable the user needs should meet the user’s needs, but after all, the user does not fully understand the details of the cable. The cable is closely related to human life, so cable manufacturers must The problem is made clear to the user.
② It is also not suitable to use a fan-shaped conductor, because the wrapping pressure of the mica tape of the fan-shaped conductor is unevenly distributed, and the pressure at the three fan-shaped corners of the fan-shaped core wrapping the mica tape is the largest. It is easy to slide between layers and is bonded by silicon, but the bonding strength is also low. , the distribution rod and the cable to the edge of the side plate of the tooling wheel, and when the insulation is extruded into the mold core in the subsequent process, it is easy to be scratched and bruised, resulting in a decrease in electrical performance. In addition, from the perspective of cost, the perimeter of the section of the fan-shaped conductor structure is larger than the perimeter of the section of the circular conductor, which in turn adds mica tape, a precious material. , but in terms of overall cost, the circular structure cable is still economical.
Based on the above description, from the technical and economic analysis, the conductor of the fire-resistant power cable adopts the circular structure as the best.