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January 4, 2021
First, wire square number and diameter conversion method knowledge
There are three common international standards for wire specifications: American (AWG), British (SWG) and our (CWG).
A few square is a nominal value set by the national standard, a few square is the user according to the load of the wire and cable to choose the wire and cable.
Electric wire square number is an oral diction in decorating hydroelectric construction, often say a few square electric wire is to did not add a unit, namely square millimeter.
The square of a wire is actually the cross-sectional area of the wire, the area of the circular cross section of the wire, measured in square millimeters.
Generally speaking, the empirical load is about one kilowatt per square wire when the grid voltage is 220V.
Copper wires can carry 1-1.5 kilowatts per square and aluminum wires 0.6 to 1 kilowatts per square.
So one square of copper wire is enough for a 1 kilowatt appliance.
Specific to the current, short - distance power transmission, the general copper wire per square can carry 3A to 5A current.
5A/ mm2 is good for heat dissipation, but 3A/ mm2 is not good.
To know the square of the wire, calculate the radius of the wire by using the formula to calculate the circular area:
The square of the wire (square mm) = PI (3.14) × the square of the radius of the wire (mm)
If you know the square of the wire, you can also calculate the diameter of the wire, as follows:
The diameter of 2.5 square wires is: 2.5÷ 3.14 = 0.8, and then the square root gives 0.9 mm, so the diameter of 2.5 square wires is: 2×0.9 mm = 1.8 mm.
To know the diameter of the wire, the square of the wire can also be calculated using the formula to find the circular area:
The square of the wire = PI (3.14) × the square of the diameter of the wire /4
The cable size is also called the square, and the multistrand is the sum of the cross-sectional areas of each conductor.
Calculation formula of cable cross-sectional area:
0.7854× radius of wire (mm) squared × number of shares
For example, 48 strands (each wire has a radius of 0.2mm) of 1.5 square lines:
0.785× (0.2 × 0.2) × 48 = 1.5 square
Second,Knowledge of commonly used small specifications of cables
RVVP: Copper conductor PVC insulated and shielded PVC sheathed soft cable, voltage 300V/300V 2-24 core.
Main quality indicators: wire diameter (including core wire and braided wire, is not the thicker the better, with copper impurity to meet resistance standards and do very thick), copper core purity, braided density, stranded distance.
Application: instrument, meter, intercom, monitor and control installation.
RG: Physical foamed polyethylene insulated access network cable is used for data analog signal transmission in coaxial fiber mixed network (HFC). This is the American standard and is approximately equivalent to the NATIONAL standard SYWV series.
Main quality indicators: copper core diameter, insulation thickness, braided materials (most of them are aluminum and magnesium wire braiding in the market, good quality should be tin-plated copper), braided density.
UTP: LAN Cable Purpose: transmission of telephone, computer data, fire, theft and security systems, intelligent building information network.
Commonly used UTP CAT 5, UTP CAT 5E with shielding model STP
KVVP: PVC sheathed braiding screened cable USES: electrical appliances, instrumentation, power distribution equipment of signal transmission, control, measuring SYWV (Y), SYKV cable TV, broadband network structure of special cable (coaxial cable) single round copper wire for anaerobic + physical foaming polyethylene (insulation) + (tin) + aluminum + PVC (PE), (equivalent to RG - 6, American standard RG - 59).
Now the market is multi-purpose aluminum-magnesium wire weaving (cannot weld, easy oxidation), the core wire with copper clad aluminum, copper clad steel, and many people think that SYWV wire is cheaper than SYV wire, but in fact is not that way.
RVV (227IEC52/53) PVC insulated flexible cable (cross-sectional area: 0.5-6.0 core cable number 1-24) Uses: power cord, signal cord, household appliances, small power tools, instruments and power lighting, etc.
This specification line as long as it conforms to the national standard price difference is not big, but there is no lack of useful impurity copper on the market, wire diameter is not enough, short meters, straight put (core copper wire or core wire is not twisted, so tensile capacity is greatly reduced, resistance increased) to recharge the situation.
Derived model: RVVS: This model of core wire stranded encryption, generally used in broadcasting systems.
Flexible cable for INSTALLATION of AVVR POLYvinyl chloride sheath (cross-sectional area: 0.12-0.5 core number 1-24) Purpose: Signal, control.
Such as access control signal, control, control and so on.
HYV and HYA data communication cables (interior and exterior) (core diameter 0.5mm, core number 2, 4, 8, etc.) namely telephone lines, used for connection of telephone communication and radio equipment and connection of branch boxes of telephone distribution network, etc.
The general diameter of the core wire on the market is 0.4 mm, but also have a handicap is to use steel wire or copper aluminum alloy.
Another telephone line is generally short of meters.
RV, RVP PVC insulated cable, PVC shielded cable, mainly used in equipment.
RVS, RVB are suitable for cable connection of household appliances, small power tools, instruments, meters and power lighting. RVS can also be used for broadcasting line or substitute RVV line.
RVB can replace gold and silver wire in the case of low requirements.
BV, BVR PVC insulated cables: suitable for fixed wiring of electrical instruments and power lighting, low resistance.
Consider this in many situations where power is connected.
At RIB speaker connections (fever wires, gold and silver wires) the models of some sound wires are often marked with the words "6N" and "7N", which is used to indicate the purity of fever wires made of metal materials.
For example, "99.9999%" can be expressed as "6N", which means it is six 9s pure. The higher the number before the N, the higher the purity of the sound line.
Whether the audio equipment of home theater needs to use high quality audio line, the key is to master the principle of seeking truth from facts and acting according to one's ability.
For the general popularization (ten thousand yuan below) audio equipment without the need to deliberately pursue the high quality of wire, as long as the use of general section of a bit larger copper core signal line can.
For better home theater audio equipment, consider using high-quality audio cables.
BVR wire is a copper core POLYvinyl chloride insulated flexible wire. It is used in fixed wiring where softness is required.
BVR wire is a kind of special flexible wire for distribution cabinet, also called secondary wire.
B refers to the distribution of wire, V refers to PVC polyvinyl chloride, commonly known as "plastic", R refers to the soft meaning, that is, increase the number of conductor roots.
Suitable for fixed installation of power plant with rated AC voltage up to and including 450/750V.
Such as home lighting.
Fixed wiring can be used for indoor open application, pipe penetration and other occasions.
In order to facilitate the difference in the installation process, it can be divided into red, yellow, blue, green, black, white and double seven colors.
Because BVR is soft structure, its application scope is mostly in soft environment.
The only difference between BVR wire and BV wire is that the conductor diameter of R-type wire is soft copper wire.
Namely: increase the number of conductor roots, reduce the diameter of a single conductor, the diameter of a single conductor is less than 1 mm.
In this way, BVR wire is very soft, laying Angle requirements than BV wire greatly reduced, threading pipe, wire groove more convenient, fast, reduce the working intensity and greatly improve the work efficiency.
By the majority of electricians and building decoration personnel like!
Fourth，Differences between BV and BVR
(1) From the production process,BV is a single core, BVR is multi-core, in the production, BVR is a bit more complex than BV.
(2) In terms of price, BVR is a little more expensive than BV.
The scope of BVR is from 2.5mm to 70mm as stipulated by the International Electrician Committee. However, according to the actual needs of China, it is the same as BV.
(3) In terms of performance, BV and BVR are basically the same, while BVR is slightly heavier in weight;
Similarly, the BVR wire can be divided into flame retardant wire (ZR-BVR), fire resistant wire (NH-BVR) and low smoke halogen-free wire (WDZ-BVR) according to the material used.
The user is flexible according to the occasion of use.
The low-smoke (low-halogen) wire produces a very small amount of smoke in the case of flame combustion. The gas released contains no halogen (low-halogen) elements and is non-toxic (low-toxic).
When the fire broke out, can greatly reduce the instruments, equipment and the harm of human body, and therefore is widely used in high-rise buildings, hospitals, large library, gym, disaster prevention command dispatch building, station and civil airport, passenger terminal, key cultural relic protection sites, as well as the subway, underground shopping mall or the densely populated public places.