First, the wire square number and diameter conversion method knowledge
There are three standards commonly used in the international wire specifications: American system (AWG), British system (SWG) and our (CWG).
A few square is a nominal value stipulated by the national standard, and a few square is the user to choose the wire and cable according to the load of the wire and cable.
The square number of wires is a verbal term in the decoration of hydropower construction, and the square number of wires is often said to be without a unit, that is, square millimeters.
The square of the wire is actually the cross-sectional area of the wire, that is, the area of the circular cross-section of the wire, in square millimeters.
In general, the experience load is when the power grid voltage is 220V, the experience load per square wire is about one kilowatt.
Copper wire can carry 1-1.5 kilowatts per square, aluminum wire can carry 0.6-1 kilowatts per square. Therefore, an appliance with a power of 1 kilowatt only needs to use one square of copper wire.
Specific to the current, the general copper wire can carry 3A to 5A current per square when the short distance is transmitted. Heat dissipation conditions are good to take 5A/ square millimeter, not good to take 3A/ square millimeter.
Conversion method:
Know the square of the wire, calculate the radius of the wire with the formula for the area of the circle:
The square of the wire (square millimeters) = PI (3.14) x the square of the wire radius (millimeters)
Know the square of the wire, calculate the diameter of the line is the same, such as:
The diameter of the 2.5 square wire is: 2.5÷3.14=0.8, and then the square is 0.9 mm, so the diameter of the 2.5 square wire is: 2×0.9 mm = 1.8 mm.
Know the diameter of the wire, calculate the square of the wire also use the formula for the circular area to calculate:
The square of the wire = PI (3.14) x the square of the wire diameter / 4
The size of the cable is also nominal in square, and the multiple strands are the sum of the cross-sectional areas of each wire.
Calculation formula of cable cross-sectional area:
0.7854 x square of wire radius (mm) x number of strands
For example, 48 strands (each wire radius 0.2 mm) of 1.5 square lines:
0.785 x (0.2 x 0.2) x 48=1.5 square
Second, commonly used small size cable knowledge
RVVP: copper core polyvinyl chloride insulated shielding polyvinyl chloride sheathed flexible cable, voltage 300V/300V2-24 core. Main quality indicators: wire diameter (including core wire and braided wire, not the thicker the better, with impurities copper to meet the resistance standard and do very thick), copper core purity, braided density, lay.
Application: instrument, instrument, intercom, monitoring, control installation.
RG: Physically foamed polyethylene insulated access network cables are used to transmit data analog signals in coaxial fiber hybrid networks (HFC), which is an American standard and approximately equivalent to the national standard SYWV series. Main quality indicators: copper core wire diameter, insulation thickness, braiding material (mostly on the market for aluminum magnesium wire braiding, good quality should use tinned copper), braiding density.
UTP: LAN cable uses: transmission of telephone, computer data, fire prevention, anti-theft security system, intelligent building information network. UTPCAT5 is commonly used, and UTPCAT5E is shielded by STP
KVVP: PVC sheathed braided shielded cable Uses: electrical appliances, meters, power distribution device signal transmission, control, measurement
SYWV (Y), SYKV cable TV, broadband network special cable structure: (coaxial cable) single oxygen-free round copper wire + physical foamed polyethylene (insulation) + (tinned wire + aluminum) + polyvinyl chloride (polyethylene), (equivalent to American standard RG-6,RG-59). Now on the market, many aluminum magnesium wire braided (can not be welded, easy to oxidize), the core wire is covered with copper aluminum, copper steel, and many people think that SYWV wire is cheaper than SYV wire, but in fact, it is not so.
RVV (227IEC52/53) PVC insulated flexible cable (cross-sectional area: 0.5-6.0 core number 1-24) Uses: power cord, signal line, household appliances, small power tools, instruments and power lighting. As long as this specification line meets the national standard, the price is not much different, but there is no shortage of useful impurity copper on the market, wire diameter is not enough, short meters, and straight (core copper wire is not twisted or core wire is not twisted, so that the tensile capacity is greatly reduced and the resistance is increased) to fill the number of cases. Derivative: RVVS: This type of core wire lay encryption, generally used in broadcast systems.
Flexible cable for installation of AVVR polyvinyl chloride sheathed (cross-sectional area: 0.12-0.5 core number 1-24) Purpose: signal, control. Such as access signal, control, PTZ control, etc.
HYV and HYA data communication cables (indoor and external) (core diameter 0.5mm, core number 2, 4, 8, etc.) are telephone lines, which are used for the connection of telephone communication and radio equipment and for the wiring of telephone distribution network distribution boxes. The general core wire diameter on the market is 0.4mm, and there are also steel wires or copper aluminum alloy. The other telephone line is generally insufficient in meters.
RV, RVP PVC insulated cable, PVC shielded cable, mainly used in equipment.
RVS, RVB are suitable for household appliances, small power tools, instruments, meters and power lighting connection cables, RVS can also be used for broadcasting lines or instead of RVV lines. RVB can replace gold and silver wire in the case of low requirements.
BV, BVR PVC insulated cable uses: suitable for electrical instrumentation equipment and power lighting fixed wiring, affordable low resistance. In many cases connected to the power supply can be considered.
RIB speaker connection line (fever line, gold and silver line) Some audio lines are often marked with the words “6N” and “7N”, which is used to indicate the purity of the fever line made of metal materials. For example, “99.9999%” can be expressed with “6N”, that is, its purity is 6 9s, and the larger the number in front of N, the higher the purity of the audio line. Whether the audio equipment of the home theater needs to use a high-quality audio cable, the key is to master the principle of seeking truth from facts and doing according to one’s ability. For the general popular type (less than ten thousand yuan) audio equipment do not need to deliberately pursue the high quality of the wire, as long as the general section of a larger copper core signal cable can be used. For better home theater audio equipment, consider using a high-quality audio cable.
Third. BVR
BVR wire is a kind of copper core polyvinyl chloride insulated soft wire, which is used in the case of fixed wiring requiring softness. BVR wire is a kind of soft wire for distribution cabinet, also called secondary wire. B refers to the classification of cloth wire, V refers to PVC polyvinyl chloride, commonly known as “plastic”, R refers to the meaning of soft, that is, to increase the number of conductor roots.
Suitable for fixed installation of power plants with rated AC voltage of 450/750V and below. Such as home decoration lighting. Fixed wiring can be used for indoor open application, pipe threading and other occasions. In order to facilitate the difference in the installation process, it can be divided into red, yellow, blue, green, black, white, double seven colors. Because BVR is soft structure, the scope of application is also mostly in soft environment. The only difference between the BVR wire and the BV wire is that the conductor of the R-type wire is soft copper wire. That is, increase the number of conductor roots, reduce the diameter of a single conductor, and the diameter of a single conductor is less than 1 mm. In this way, the BVR wire is very soft, the laying Angle requirement is greatly reduced than the BV wire, the threading pipe and the wire slot are more convenient and fast, and the work intensity is reduced while the work efficiency is greatly improved. By the majority of electricians and building decoration personnel like!
Fourth, the difference between BV and BVR:
(1) From the production process,BV is single core, BVR is multi-core, in the production, BVR is a little more complex than BV.
(2) In terms of price, BVR is a little more expensive than BV. In the International Electrotechnical Commission, the range of BVR is from 2.5mm to 70mm, but according to the actual needs of our country, it is the same as BV.
(3) In terms of performance, BV and BVR are basically the same, and BVR is slightly heavier in weight;
Similarly, BVR wires are also divided into flame retardant wires (ZR-BVR), fire-resistant wires (NH-BVR), and low smoke halogen-free wires (WDZ-BVR) according to the material selected. Users can master it flexibly according to the occasion of use. Among them, the low-smoke no (low) halogen wire produces a very small amount of smoke in the case of flame combustion, and the released gas does not contain halogen (low halogen) elements, and is non-toxic (low toxic).
When a fire occurs, it can greatly reduce the harm to instruments, equipment and the human body, so it is widely used in high-rise buildings, hospitals, large libraries, gymnasiums, disaster prevention command and dispatch buildings, stations and civil airports, passenger waiting rooms, key cultural relics protection places and subways, underground shopping malls or densely populated public places.
Post time: Dec-12-2023