Broad wire and cable are also referred to as cables. A narrow cable refers to an insulated cable. It can be defined as: an aggregate consisting of one or more insulated cores, and their respective cladding layers, total protective layer and outer sheath. The cable may also have additional conductors that are not insulated. Cable type and selection calculation

First, the definition and classification of cables Broadly defined wire and cable is also referred to as cable. A narrow cable refers to an insulated cable. It can be defined as: an aggregate consisting of one or more insulated cores, and their respective cladding layers, total protective layer and outer sheath. The cable may also have additional conductors that are not insulated.



China's wire and cable products are divided into the following five categories according to their purposes:
1. bare wire 2. winding wire 3. power cable 4. communication cable and communication cable 5. wire and cable for electrical equipment

The basic structure of wire and cable:
1. Conductor The object that conducts current, the specification of the wire and cable is represented by the cross section of the conductor.
2. Insulation The thickness of the outer insulation material according to its withstand voltage

Second, the working current and calculation of the electric (line) cable operating current calculation formula:
Simplex
I=P÷(U×cosΦ)
P-power (W); U-voltage (220V); cosΦ-power factor (0.8); I-phase current (A)

Three phase
I=P÷(U×1.732×cosΦ)
P-power (W); U-voltage (380V); cosΦ-power factor (0.8); I-phase current (A)

The safe cut-off flow of a typical copper wire is 5-8 A/mm 2 , and the safe cut-off flow of an aluminum wire is 3-5 A/mm 2 .
In a single-phase 220V line, the current per 1KW power is about 4-5A. In a three-phase load balanced three-phase circuit, the current per 1KW power is about 2A.
That is to say, in a single-phase circuit, each 1 mm square copper wire can withstand 1 KW power load; the three-phase balanced circuit can withstand 2-2.5 KW power.
However, the larger the operating current of the cable, the smaller the safe current that can be tolerated per square millimeter.

The safe working current port allowed by the cable:
Tenth five (10 times or less by five)
One hundred and two (more than one hundred times two)
Two five three five four three three circles (two five times four, three five times three)
Two and a half times seven zero nine five (the seven zero and nine five lines are multiplied by two)
The temperature of the tube is 80% off (changes with temperature, multiplied by the number of safe currents by 0.8 or 0.9)
Copper wire upgrade calculation (in the same section of the aluminum core line rises one level, such as 2.5 copper wire is one step up in the aluminum alloy wire, then four square millimeter aluminum core wire)
Add half of the bare wire (add half of the original safe current number)

Third, commonly used electric (line) cable type cable specification model meaning:
In the wire model: the letter B indicates the cloth wire, the letter V indicates the polyvinyl chloride in the plastic, and the letter R indicates the soft wire (the conductor is a plurality of filaments twisted together). Also, the copper core symbol and the hard line (common single core conductor) are omitted and not shown.
Common cable types:
BV- means single copper core PVC insulated wire, no sheathed wire. Applicable to wire and cable for power equipment, household appliances, instrumentation and telecommunications equipment with AC voltages of 450/750V and below.
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BVR- indicates PVC insulated, copper (soft) cloth wire, often referred to as soft wire. Because the wires are soft, they are often used in electric power dragging and motor connections, as well as where the wires often move slightly.
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BVV- indicates a copper core PVC insulated PVC round sheathed cable and a copper core (hard) cloth wire. Often referred to as sheathed wire, single core is round, double core is flat, often used for surface mounted wires.
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BVVB- represents a copper core PVC insulated PVC flat sheathed cable. Applicable to the requirements of high mechanical protection, moisture, etc. can be applied or dark.
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SYV-solid polyethylene insulated RF coaxial cable. Suitable for closed circuit monitoring and cable TV engineering.
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RG- denotes a physically foamed polyethylene insulated cable, commonly used in coaxial fiber-optic hybrid networks (HFC) to transmit data analog signals, as well as video transmission, communication systems and signal control systems.
SYWV-physical foaming polyethylene insulated cable TV cable, video (RF) coaxial cable (SYV, SYWV, SYFV) for closed-circuit monitoring and cable TV engineering.
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Structure: (coaxial cable) single oxygen-free round copper wire physical foaming polyethylene (insulation) (tin wire aluminum) polyvinyl chloride (polyethylene)
RVV- indicates a copper core PVC insulated PVC sheathed round connection flexible cable. Applicable to building intercom, anti-theft alarm, fire protection, automatic meter reading and other projects.
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RVVP- indicates a soft copper core stranded round PVC insulated and insulated PVC sheathed flexible wire. Applicable to building intercom, anti-theft alarm, fire protection, automatic meter reading and other projects.
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BVVP- indicates a hard copper core flat PVC insulated PVC sheath and a copper mesh shielded wire.
RVS- indicates a copper core PVC stranded connection wire. Commonly used in household appliances, small power tools, instrumentation, control systems, broadcast audio, fire, lighting and control lines.
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VV(VLV)- indicates copper (aluminum) core PVC insulated PVC sheathed power cable, suitable for laying in indoors, tunnels, and trench pipes. It can not bear the mechanical external force and can be directly buried.
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Cable model definition:
PVC insulated and shielded PVC sheathed flexible cable
Soft cable (wire) for R-connection, soft structure.
V-insulated polyvinyl chloride
V-polyvinyl chloride insulation
V-polyvinyl chloride sheath
B-flat (flat)
S-twisted type
A-tinned or silver plated
F-high temperature resistance
P-woven shield
P2-copper tape shielding
P22-steel tape armor
Y—prefabricated, generally omitted, or polyolefin sheath
FD—Product category code, refers to the branch cable. The Ministry of Construction standards to be promulgated are indicated by FZ, which are essentially the same
YJ - XLPE insulation
V—polyvinyl chloride insulation or sheath
ZR—flame retardant
NH-refractory type
WDZ - halogen-free low smoke flame retardant
WDN - halogen free low smoke fire resistant

RV copper core vinyl chloride insulated connecting cable (wire)
AVR tinned copper core PE insulated flat connection flexible cable (wire)
RVB copper core PVC flat connecting wire
RVS copper core PVC stranded connecting wire
RVV copper core PVC insulated PVC sheathed round connection flexible cable
ARVV tinned copper core PVC insulated and PVC sheathed flat connection flexible cable
RVVB copper core PVC insulated and PVC sheathed flat connection flexible cable
RV-105 copper core heat-resistant 105oC PVC insulated PVC insulated flexible cable
AF-205AFS-250AFP-250 Silver plated polyvinyl chloride plastic insulation high temperature resistant -60oC~250oC connection flexible wire

Fourth, the power cable is suitable for AC 50HZ, rated voltage 0.6/1KV and below transmission and distribution lines for power transmission and distribution. The ambient temperature is 25 ° C and the cable conductor operating temperature does not exceed 70 ° C.
VV (VLV) copper (aluminum) core PVC insulated PVC sheathed power cable, suitable for laying indoors, tunnels, and trench pipes, can not withstand the external force of the machine, can be directly buried.
VY (VLY) copper (aluminum) PVC insulated and sheathed power cable for indoor, pipeline and pipeline
VV22(VLV22) Copper (aluminum) core PVC insulated poly steel tape armored PVC sheathed power vv22 cable, same VV type, can be buried directly in the soil to withstand mechanical external forces, can not withstand large tensile forces.
VV23 (VLV23) copper (aluminum) core PVC insulated poly steel tape armored PE sheathed power cable, same as VV2 type.
ZRVV22 is the same as VV22 type, which is suitable for occasions with flame retardant requirements.
YJV copper core XLPE insulated PVC sheathed power cable
YJV copper core XLPE insulated steel tape armored PVC sheathed power cable
NHVV and VV type are suitable for applications with fire resistance requirements.
KVV PVC insulated control cable use: electrical, instrumentation, power distribution equipment signal transmission, control, measurement.
NH-*** fire resistant power cable
ZR-*** flame retardant power cable
WDZ-*** Low Smoke Zero Halogen Power Cable

5. Cable model definitions such as:
BV4
Single copper core PVC insulated wire with a copper core cross-section of 4 mm2.

SYV 75-5-1 (A, B, C)
S: RF Y: Polyethylene insulation V: PVC sheath A: 64, B: 96, C: 128
75:75 ohms 5: wire diameter is 5MM 1: represents single core

SYWV 75-5-1
S: RF Y: Polyethylene insulation W: Physical foaming V: PVC sheath
75:75 ohms 5: cable outer diameter is 5MM 1: represents single core

RVVP2*32/0.2 RVV2*1.0 BVR
R: Cord VV: Double sheathed wire P shield
2: 2 core multi-strand line 32: 32 copper wires per core 0.2: each copper wire diameter is 0.2MM

ZR-RVS2*24/0.12
ZR: Flame retardant R: Cord S: twisted pair
2: 2 core multi-strand wire 24: 24 copper wires per core 0.12: each copper wire diameter is 0.12MM

ZR-BVV 3x6.0
Represents three copper core PVC insulated PVC round sheathed cables with a cross section of 6 mm2.

NH-VV 3x70+2X35
It is a refractory PVC insulated and PVC sheathed power cable with three cross-sectional areas of 70mm2 copper core and two 35mm2 copper cores.

2, the meaning of the specification means the specification uses the number of cores, the nominal section and the voltage level to indicate the specification of a single-core branch cable: the number of cables in the same loop * (1 * nominal section), 0.6 / 1KV,
Such as: 4*(1*185)+1*95 0.6/1KV
2 multi-core stranded branch cable specification: the number of cables in the same loop * nominal cross section, 0.6/1KV,
Such as: 4**185+1*95 0.6/1KV
3 multi-core and sheathed branch cable specification: cable core number × nominal cross section -T, such as: 4 × 25-T

Sixth, other common sense:
1. Calculation formula of wire cross-sectional area (wire distance / pressure drop / current relationship)
Copper wire S=IL÷ (54.4×U)

Aluminum wire S=IL÷(34×U)
Maximum current through the I-wire (A); L-wire length (m); U-allowable pressure drop (V); S-wire cross-sectional area (mm 2 )

2. Wire and cable basics
1. The length of the wire is 100 meters, and the positive and negative error is 0.5 meters;
2. Wire model: BV single-share, BVR multi-share, BVV double-glue single-share, BVVR double-glue multiple shares;
3. Common specifications of wire: 1 square / 1.5 square / 2.5 square / 4 square / 6 square / 10 square, etc.;
4.BV/BVR difference: BV is single core wire, BVR is multi-strand, BVR is about 10% more expensive than BV;
5.BVR has better benefits than BV: a hydropower construction is convenient. b is not easy to break the line when the plate is bent;
6. National standard GB4706.1-1992/1998 specified wire load current value (partial)
7. Home circuit design, 2000 years ago, the circuit design is generally: 4-6 mm2 into the household line, 1.5 mm2 lighting, 2.5 mm2 socket, 4 mm2 air conditioning. After 2000, the circuit design is generally: 6-10 mm2 for the incoming line, 2.5 mm2 for the lighting, 4 mm2 for the socket, and 6 mm2 for the air conditioner.
8. Wire weight: 1.5 square meters weighs 2.2 kilograms, 2.5 weighs 3.2 kilograms, 4 squares weighs 4.8 kilograms, and 6 squares weighs about 6.5 kilograms.
9. The multi-strand line (1 square, 1.5 square) of the wire below 2.5 square is marked as BV (B), and the single strand is BV.
10. Wire color: red, yellow, blue, green, black, yellow green (ground)

Http://news.chinawj.com.cn Editor: (Hardware Business Network Information Center) http://news.chinawj.com.cn

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