1. Temperature
The higher the temperature, the lower the current carrying capacity of the wire. This is the most common problem and the main reason why building cables need to be thicker than the cables used in the strip. Moreover, in many cases, the ambient temperature is uncontrollable. The ventilation effect, sunlight conditions, and the density of cables will all affect the ambient temperature, which in turn affects the current carrying capacity of the cables.
2. Cable density
Too dense cable laying will not only create excessive temperature. When multiple wires are laid in parallel, the proximity effect and the skin effect will also be formed, so that the electric charge is concentrated in the section of the wire and the allowable current carrying capacity of the wire is reduced.
3. Length
The longer the cable, the lower the ampacity. The difference between the current carrying capacity of a 100-meter cable and the current carrying capacity of a 10,000-meter cable is not an order of magnitude.
(Because my fans pay more attention to the home decoration circuit, so I want to say a little more here: the above-mentioned external factors that affect the current carrying capacity of the wires are mostly for power transmission, industry, and commercial use. , The distance is short, so the influence of external factors on the cable can be ignored.)
Internal factors that affect wire current carrying capacity:
In addition to some external factors that will reduce the current carrying capacity of the cable in a specific environment, the more important factor that can determine the current carrying capacity of the wire is the internal factors of the wire, which are mainly determined by the following three points:
1. Core area
That is, the "wire diameter" we often say, such as 2.5 square millimeters, 4 square millimeters, etc., which are common in decoration, all of which are wire diameters. It's just that the following is emphasized here. It is not the cross-sectional area of the entire wire that determines the current-carrying capacity, but the cross-sectional area of the conductor inside the wire. The thicker the wire, the greater the current carrying capacity.
2. Material conductivity
Here it depends on the conductor material, such as common copper wire and aluminum wire. The conductivity of copper material is at least 30 percent higher than that of aluminum. And when necessary, silver lines may also appear. In addition to the substance of the material, it also depends on the purity of the material. Taking copper as an example, red copper with the highest purity has a much higher conductivity than the second-class brass.
3. Thermal conductivity of insulating layer
The role of the insulating layer, in addition to preventing electric shock, also has a function as important as preventing electric shock - flame retardant. The better the thermal conductivity of the insulating layer material, the better the flame retardant performance. Therefore, the quality of the insulating material determines the current carrying capacity of the wire from another aspect.
