Indoor low-voltage cable is installed for the transmission low voltage alternating current wires in the indoor, The indoor voltage is more 220V or 380V, the former is used for lighting and household appliances, the latter is used in three-phase power equipment. The two purposes are different, but the power supply line, cable selection principle and method are the same. Indoor cable selection, the main consideration should be given to the following four aspects:
1. Sufficient mechanical strength and flexibility
Must have sufficient mechanical strength and flexibility. The mechanical strength is too small, cannot afford to pull people easy to break out. The concealed way installation, cables through the pipe fixed in the wall, if the mechanical strength is insufficient, threading process may cause broken wire core, so, bright or dark outfit fix cables with single copper core or the aluminum core wire.
The power line of the household appliances or temporary socket leads, because often plug mobile, the softness of the cable should be mainly considered, the general should choose multi stranded copper core.
The insulation performance of the cable is an important index to ensure the safe use of electricity. There are two kinds of insulation of common cable: Rubber and plastic. Rubber insulated wire for AC rated voltage below 250V, the long-term working temperature does not exceed 60℃ occasions. Plastic insulated wire, for AC rated voltage 500V voltage or DC voltage below 1000V, working temperature for a long time does not exceed 65℃ occasions.
3. electrical conductivity
High conductivity copper, aluminum times, under the same resistance, wire section is 1.68 times that of copper wire, copper wire mechanical strength was higher than that of the aluminum; aluminum price is low, not easy to weld.
4. the cross-sectional area of the cable
Correctly selecting the conductor cross-sectional area of the cable is one of the most important measures to ensure the safety, reliability and economy.
Cable safe ampacity, depending on the conductor material and section area of the, determining the conductor material, sectional area is first should be considered. Higher conductivity of the conductor in the cable, the bigger the section area and the safe flow is bigger, and the cable insulation material, laying mode, environment temperature and so on. A lot of people in full consideration of the above factors in practice, to sum up the common cable safety and look-up table.
According to the maximum current of the load used by the user, the conductor material and the way of laying, the corresponding wire cross section can be found out from the table. The principle is: the wire of the safe carrying capacity is equal to or slightly greater than the actual strength of the current.
In the scope of the possible, the cross-sectional area of the wire should follow the principle of better not small, just have a larger safety factor.