Cable for unshielded twisted pair (UTPs), support for high-definition video transmission and accurate data transmission and KVM (keyboard, monitor and mouse) technology, is the best solution for professional video and data applications, The video application provides excellent low offset performance, conforms to and applies to the TIA / EIA standard.
Buy common sense
1, look at the "CCC" certification logo. Therefore, the cable product is a national compulsory safety certification products, all production enterprises must obtain the China Electrotechnical Product Certification Committee certified "CCC" certification, access to "CCC" certification mark, in the certificate or product on the "CCC" certification mark.
2, look at the inspection report. Cable as the impact of personal and property safety products, has been listed as the focus of government supervision and inspection, regular manufacturers by the cycle to accept the supervision department inspection. Therefore, the seller should be able to provide a quality inspection department inspection report, otherwise, the quality of cable products on the basis of lack of quality.
3, pay attention to packaging. Wire and cable products, like other products, all products, in line with national standards for the production of large and medium-sized formal enterprises, the production of cable is very focused on product packaging. When purchasing attention to packaging to be fine, print to be clear, model specifications, factory name, site and so complete.
4, look at appearance, product appearance smooth round, uniform color. Products meet the national standard requirements of the cable business, in order to improve product quality, to ensure that products meet national standards, in the purchase of raw materials, production equipment, production processes, and other strict checks. Therefore, the production of wire and cable products meet the standard requirements: smooth round, uniform color. While the appearance of counterfeit inferior cable is rough and dull. And for the rubber insulated flexible cable, requiring the appearance of round, jacket, insulation, the conductor is not easy to peel off. The counterfeit inferior product appearance rough, large oval, jacket insulation strength is low, hand can tear off.
5, see conductor, conductor shiny, DC resistance, conductor structure size in line with national standards. In line with the national standard requirements of the wire and cable products, whether aluminum material conductor, or copper material conductors are relatively bright, no oil, so the conductor of the DC resistance in full compliance with national standards, with good electrical conductivity, high security.
6, the amount of cable length. The length is the main intuitive way of distinguishing products that meet the requirements of national standards and counterfeit inferior products. When buying, do not covet the cheap, choose to have 90m or 80m, or even no length of the identification of the wire and cable, the length must meet the 100 ± 0.5m standard requirements, that is 100 meters as the standard, allowing the error of 0.5 meters).
Calculation of cross - sectional area and current carrying capacity of conductor
First, the general copper wire carrying capacity of the safe flow of the wire is based on the maximum allowable core temperature, cooling conditions, laying conditions to determine. Generally, the safe current carrying capacity of copper wire is 5 ~ 8A / mm2, and the safe current of aluminum wire is 3 ~ 5A / mm2. <Key points> General copper wire safety current carrying capacity of 5 ~ 8A / mm2, aluminum wire safety current carrying capacity of 3 ~ 5A / mm2. Such as: 2.5 mm2 BVV Recommended recommended for safe current carrying in the copper conductor 2.5 × 8A / mm2 = 20A 4 mm2 BVV Recommended recommended for safe carrying of copper conductors 4 × 8A / mm2 = 32A
Second, calculate the copper conductor cross-sectional area of the use of copper wire safety carrying capacity of the recommended value of 5 ~ 8A / mm2, calculate the selected copper wire cross-sectional area S range: S = <I / (5 ~ 8)> = 0.125 I ~ 0.2 I (mm2) S ----- copper wire cross-sectional area (mm2) I ----- load current (A)
Third, the power calculation of the general load (can also be used as electrical appliances, such as lighting, refrigerator, etc.) is divided into two kinds, a resistive load, one is the inductive load. For the resistive load calculation formula: P = UI for the fluorescent lamp load calculation formula: P = UIcosф, where the fluorescent lamp power factor cosф = 0.5. Different inductive load power factor is different, unified calculation of household appliances can be power factor cosф take 0.8. That is, if a household with all the electrical appliances with a total power of 6000 watts, the maximum current is I = P / Ucosф = 6000/220 * 0.8 = 34 (A) However, under normal circumstances, home appliances can not be used at the same time , So add a common coefficient, the common coefficient is generally 0.5. Therefore, the above calculation should be rewritten as I = P * common coefficient / Ucosф=6000*0.5/220*0.8=17 (A) In other words, the total current value of the family is 17A. The total gate air switch can not use 16A, should be greater than 17A.