Square of plastic cable

1.

There are two kinds of square number of cables: one is calculated according to the diameter, that is, the square of 3.14 * r, and the other is calculated according to the DC resistance, which is more troublesome, and most of the experimental data

Generally speaking, when the grid voltage is 220 V, the empirical load per square wire is about one kilowatt

copper wire can carry 1-1.5 kW per square meter, and aluminum wire can carry 0.6-1 kW per square meter. Therefore, an electric appliance with a power of 1 kW only needs one square of copper wire

when it comes to current, copper wire can carry 3a to 5A current per square meter in short distance transmission. If the heat dissipation condition is good, 5A / mm ~ 2, but not 3A / mm ~ 2

conversion method:

know the square of the wire, and calculate the radius of the wire with the formula of circular area:

wire square (square millimeter) = (3.14) × The square of wire radius

knowing the square of wire, calculating wire diameter is the same, for example:

2.5 square wire diameter is: 2.5 ÷ 3.14 = 0.8, and then square out to get 0.9 mm, so the line diameter of 2.5 square line is: 2 × 9 mm = 1.8 mm

knowing the diameter of the wire, the square of the wire can also be calculated by the formula of circular area:

square of the wire = circumference (3.14) × The square / 4 of the wire diameter is also used as the nominal cable size, and the multi strand wire is the sum of the cross-sectional areas of each wire

calculation formula of cable cross section area:

0.7854 × Square of wire radius (mm) × Number of strands

for example, 48 strands (wire radius 0.2mm per strand) of 1.5m2 wire:

0.7854 × zero point two × 0.2 × 48 = 1.5 square

extended data:

the square of wire can be measured and calculated by wire diameter, because wire diameter is better measured,

formula is s = 3.14d/4; D is the diameter

There is an estimation formula for

carrying capacity, which is posted for your reference:

ten times five; Two in a hundred; Two five three five four three boundaries

70952; 90% of the pipe temperature

0; Bare wire plus half

note:

five under ten means five times less than ten

two in a hundred means more than one hundred times two

Two five three five four three boundaries are two five times four, three five times three

Two and a half times of 7095 means that the lines of 7095 and 95 are multiplied by 2.5

the 20% discount of the tube temperature is that it changes with the change of temperature, multiplying the calculated safe current by 0.8 or 0.9

copper wire upgrade calculation is to increase one level on the basis of aluminum core wire with the same cross section. If 2.5 copper core wire is to increase one level on the basis of 2.5 aluminum core wire, it is calculated as 4 square millimeter aluminum core wire Computer cable, signal cable, coaxial cable, fire resistant cable, marine cable, mining cable, aluminum alloy cable, etc. They are composed of single or multiple strands of wire and insulation layer, used to connect circuits, electrical appliances, etc

According to the system of photovoltaic power station, cables can be divided into DC cables and AC cables, which can be classified as follows according to different uses and environments:

1. DC cables

(1) series cables between moles

(2) parallel cables between strings and between strings and DC distribution box (junction box)

(3) cable between DC distribution box and inverter

all the above cables are DC cables, which are laid outdoors and need to be moisture-proof, sun proof, cold resistant, heat-resistant, UV resistant, and acid-base and other chemicals in some special environments

AC cable (1) connecting cable from inverter to step-up transformer

(2) connecting cable from step-up transformer to power distribution device

(3) the connecting cable from the power distribution device to the power grid or users

this part of the cable is AC load cable, which can be selected according to the requirements of general power cable selection

When the cables cross each other, the high-voltage cable should be under the low-voltage cable. If one of the cables is protected by pipe or separated by partition within 1m before and after the intersection, the minimum allowable distance is 0.25m

The minimum distance of parallel and cross is 0.5m and 0.25m respectively when the cable is close to or cross with the heat pipe, if there are heat insulation measures

When the cable crosses the railway or road, it should be protected through the pipe, and the protective pipe should extend 2m beyond the track or road

The distance between the cable and the building foundation should ensure that the cable is buried outside the building apron; When the cable is introced into the building, it should be protected through the pipe, and the protective pipe should also be beyond the building apron

The distance between the cable directly buried underground and the grounding of general grounding device should be 0.25 ~ 0.5m; The buried depth of cables directly buried in the ground should not be less than 0.7m in general, and should be buried under the permafrost

storage method

if the cable is to be stored for a long time, the following considerations should be considered according to the location of the cable:

1. Under the eaves. The standard LAN cable can be used only when the cable is not directly exposed to sunlight or ultra-high temperature. It is recommended to use pipes

2. Avoid direct sunlight on the wall and man-made damage

3. In pipes (plastic or metal). For example, in pipes, pay attention to the damage of plastic pipes and the heat conction of metal pipes

4. Suspended application / overhead cable. Considering the sagging and pressure of the cable, which binding method is to be adopted, and whether the cable is directly exposed to sunlight

When the cable is laid directly in the underground cable trench, the control range is the smallest. The installation of cable trench shall be checked for dryness or humidity regularly

6. Underground pipeline. In order to facilitate future upgrading, cable replacement and isolation from surface pressure and surrounding environment, auxiliary pipeline is a better method. But don't expect that the pipe will stay dry forever, which will affect the choice of cable type

2.

Conventional calculation method for weight of cable without conversion: sectional area * 8.89 = kg / km, such as 120 square mm calculation: 120 * 8.89 = 1066.8kg/km

1, sheath thickness: outer diameter before extrusion × 035 + 1 (according to the power cable, the nominal thickness of single core cable sheath shall not be less than 1.4mm, and that of multi-core cable shall not be less than 1.8mm)

2. Online measurement of sheath thickness: sheath thickness = (perimeter after extruding sheath - Perimeter before extruding sheath) / 2 π Or sheath thickness = (perimeter after sheath extrusion - Perimeter before sheath extrusion) × 1592

3. Steel wire armoring: number of pieces = 0{ π× Sheath outer diameter + thread diameter)} thread diameter ×λ Weight (quantity)= π× Wire diameter 2 ×ρ× L × number ×λ

Weight of insulation and sheath= π× Outer diameter + thickness before extrusion) × thickness × L ×ρ

5{ π× Outer diameter before package + 2 × Thickness - 1) × two × thickness ×ρ× 50} (1 + k)
6{ π× Outer diameter before wrapping + number of layers × Thickness) × Number of layers × thickness ×ρ× L /1 ± K) Where: K is the overlap ratio or gap ratio; if it is overlap, it is 1-k; If it is a gap, it is 1 + K; ρ Is the specific gravity of the material; L is the length of the cable; λ It's a distortion factor

extended data

the cable is composed of one or more insulated wires covered with tough metal or rubber outer layer. Cables and wires are usually composed of cores, insulating sheaths and protective covers

The characteristics of common cable are as follows: CEF - EPDM insulation, chloroprene rubber sheath, marine flame retardant power cable. CVV - PVC insulated PVC sheathed marine flame retardant power cable. BV, BX, RV, RVV series wires are often used in oxygen tank line

where: bv - copper core PVC insulated wire, long-term allowable temperature 65 ℃ ° C. Minimum temperature - 15 ° C. Working voltage AC 500V, DC 1000V, indoor and outdoor fixed laying, can be applied or avoid light. BX -- copper core rubber insulated wire, maximum temperature 65 ℃ ° C. Suitable for indoor use

RV - PVC insulated single core wire, the maximum working temperature is 65 ℃ ° C. The minimum working temperature is - 15 ℃ ° C. Working voltage is AC 250V, DC 500V, used for internal wiring of instruments and equipment

RVV -- copper core PVC insulated and sheathed flexible wire, allowable long-term working temperature 105 ℃ ° C. Working voltage AC 500V, DC 1000V, suitable for wet, high mechanical protection requirements, often moving and bending occasions. In fact, there is no strict line between "wire" and "cable"

3. 95 square copper core cable can carry 168 kW equipment
determine the safe current carrying capacity of the cable according to the formula. 95 square copper core is calculated as 120 square aluminum core, the current carrying capacity of 120 square conctor is 2.5 times of its cross-sectional area, so 120x2.5 = 300A. The total power is calculated as follows:
P = 1.732uicos φ= 1.732x0.38x300x0.85=168kW According to the calculation of three-phase commercial power, cos φ Is the power factor, generally 0.85)
the formula of safe current carrying capacity of aluminum cable is:
2.5 times 9, up minus 1
35 times 3.5, double double group minus 0.5
the conditions are as follows: conversion of change and addition, upgrading of high temperature copper
the number of tubes is two three four, eight seven six
the first sentence of the formula means: the current carrying capacity of aluminum core insulated wires with various cross sections of 2.5 square meters or less is 9 times of the number of cross sections. Such as 2.5 square conctor, the current carrying capacity is 2.5 × 9=22.5(A) The multiple relationship between the current carrying capacity and the number of cross-sections of conctors with a square area of 4 or more is arranged upward along the line number, and the multiple is successively reced by 1, i.e. 4 × 8、6 × 7、10 × 6、16 × 5、25 × 4
the second sentence of the pithy formula means: the current carrying capacity of 35 square wires is 3.5 times of the number of cross sections, that is 35 × 3.5=122．5(A) From the multiple relationship between the current carrying capacity and the number of cross-sections of the conctor with an area of 50 square meters or more, it becomes a group of two wire numbers, and the multiple is reced by 0.5 in turn, that is, the current carrying capacity of the conctor with an area of 50 and 70 square meters is 3 times of the number of cross-sections, and the current carrying capacity of the conctor with an area of 95 and 120 square meters is 2.5 times of the number of cross-sections, and so on
the third sentence of the formula means: the applicable conditions of the formula are "aluminum core insulated wire, single open laying, ambient temperature 25 ℃". If the aluminum core insulated wire is exposed in the area where the ambient temperature is higher than 25 ℃ for a long time, the current carrying capacity of the wire can be calculated according to the above formula, and then 10% off. When copper core insulated wire is used instead of aluminum wire, its current carrying capacity is slightly larger than that of aluminum wire of the same specification. According to the above formula, the current carrying capacity of one wire number larger than that of aluminum wire can be calculated. For example, the current carrying capacity of 16 square copper wire can be calculated as that of 25 square aluminum wire
the fourth sentence of the formula means: in the case of laying two, three or four wires through pipes, the current carrying capacity is calculated as 80%, 70% and 60% of the current carrying capacity (single wire laying) in the formula.

4.

If you want to judge the thickness (square) of the wire, you can use a vernier to measure the diameter of the wire, and then calculate the cross section

section formula: S = square of radius r?? ×π R is the radius of the wire)

for example, a wire with a diameter of 1.76 is 1.76 ÷ two × 3.14 = 2.76 square ≈ 2.5 square (approximate)

if you want to choose the size of the wire, you should first calculate the current according to the power of the electrical appliance, and then check the electrician manual according to the current, which is more accurate

if it is a single core, its diameter can be measured, and then the radius can be obtained

according to the formula of area s = radius * radius * 3.14

the cross-sectional area of the wire can be known, and some wires are twisted together by multiple cores, so it can't be calculated by single core method, but can only be calculated by connecting single core wire according to one of multiple wires in the wire, Then multiply it by the number of shares in the line

The formula is s = radius * radius * 3.14 * n, where n is the number of twisted wires

extended data

conversion relationship between wire square number and current

safe current carrying capacity of 2.5 square millimeter copper power line-28a

The safe current carrying capacity of

4mm2 copper power line is 35A

The safe current carrying capacity of

6mm2 copper power line is 48A

The safe current carrying capacity of

10 square millimeter copper power line is - 65A

the safe current carrying capacity of 16mm2 copper power line is - 91A

The safe current carrying capacity of

25 square millimeter copper power line is - 120a

for aluminum wire, the wire diameter should be 1.5-2 times of copper wire

if the current of copper wire is less than 28a, it is safe to take 10A per square millimeter

if the current of copper wire is greater than 120a, take 5A per square millimeter

5. The square number of the cable can be calculated as follows:
1. First calculate the rated current of the circuit
2. Determine the cable size according to the current value< The pithy formula of selecting cable according to current:
10 lower five, 100 upper two,
25, 35, 4, 3,
70, 95, twice and a half
pipe penetration, temperature, 20% or 10% discount
bare wire plus half
copper wire upgrade calculation
the formula does not directly point out the current carrying capacity (safety) of various sections, but expresses it by multiplying the section by a certain multiple. The specifications of nominal cross-section (mm 2) of wires commonly used in China are:
1, 1.5, 2.5, 4, 6, 10, 16, 25, 35, 50, 70, 95, 120, 150, 185...
Part I
(1) the first formula points out that the current carrying capacity (a) of aluminum core insulated wire can be calculated by multiple of cross-section. The Arabic numerals in the pithy formula represent the cross section of the wire (square millimeter), and the Chinese numerals represent the multiple. The relationship between cross section and multiple of the formula is as follows:
(1-10) square: five times
16,25 Square: four times
35,50 Square: three times
70,95 Square: two and a half times
120 square and above: two times
for example, the calculation of current carrying capacity of aluminum core insulated wire when the ambient temperature is not more than 25 ℃:
when the cross section is 6 square mm, The calculated ampacity is 30 a
when the cross section is 150 square mm, the current carrying capacity is 300 a
when the cross-section is 70 square mm, the current carrying capacity is 175 a< (2) the last three pithy formulas are the treatment of conditional change“ The "20% or 10% discount" for pipe laying and temperature refers to: in case of pipe laying (including trough plate laying, i.e. the conctor is covered with protective cover and is not exposed), 20% discount will be given after calculation; If the ambient temperature exceeds 25 ℃, 10% discount will be given after calculation; if the temperature exceeds 25 ℃ after laying through pipes, 10% discount will be given after 20% discount, or 70% discount will be given at a time
the third part
(3) for the current carrying capacity of bare aluminum wire, the formula points out that "half of bare wire is added", that is, half is added after calculation. This means that the current carrying capacity of bare aluminum wire with the same section can be increased by half compared with that of aluminum core insulated wire< The fourth part (4) for the current carrying capacity of copper conctor, the pithy formula points out "copper wire upgrade calculation", that is to say, the cross-section order of copper conctor is upgraded by one level, and then calculated according to the corresponding aluminum wire conditions.

6. The simplest calculation method is the formula of current carrying capacity of cables commonly used by electricians: different materials (copper or aluminum), different wire diameters, different load currents. The simplest calculation method can refer to the formula: 10 under five, 100 on two; 25,35,4,3; Two and a half times of 70 and 95; Through the tube, the temperature is 80% or 90%; Bare wire plus half; Copper wire upgrade
10 the lower five means that the safe current carrying capacity of less than 10 square wires is five times of the wire diameter, for example, the safe current carrying capacity of 6 square millimeter aluminum core wires is 30A
100, the upper two means that the safe current carrying capacity of more than 100 square wires is twice of the wire diameter, for example, the safe current carrying capacity of 150 square aluminum core insulated wires is 300A
25 The current carrying capacity of 35 square to 25 square aluminum core insulated wires is four times of the wire diameter, and that of 35 square to 70 square wires (excluding 70) is three times
two and a half times of 70 and 95 means that the safe current carrying capacity of 70 square and 95 square aluminum core insulated wires is two and a half times of the wire diameter
"pipe laying, temperature, 20% discount" refers to if the pipe laying (including slot plate, etc., that is, the line is covered with protective cover) is not exposed, 20% discount (multiply by 0.8) shall be given after calculation according to the above method. If the ambient temperature exceeds 25 ℃, 10% discount will be given according to the above line diameter method. For the two conditions of pipe temperature at the same time, the safe current carrying capacity is calculated as the above wire diameter, which is converted by seven times
bare wire plus half means that the safe current carrying capacity of bare aluminum wire with the same section is 1.5 times that of insulated aluminum core wire
copper wire upgrade calculation means that the cross section of copper wire is upgraded by one level according to the cross section of aluminum core wire, and then calculated according to the corresponding conditions of aluminum core wire

7. Because the welding machine has a temporary load rate, the calculated power of the welding machine can not be calculated according to the rated power of the welding machine. There are commonly used demand factors in the design manual. If your welding machine is manual welding machine, then the sum of the rated capacity of all welding machines multiplied by the coefficient of 0.35, based on the power, calculate the current, and then select the cable according to the current. When selecting cables, consider the cable laying mode, the highest ambient temperature, the number of parallel cables when laying, and then give the cable ampacity correction factor to determine the cable section
in addition, your welding machine is single-phase, so you should try to balance the distribution on the three phases, and calculate the three-phase load according to the single-phase load calculation method. Refer to the instrial and civil power distribution design manual.

8. The square number written on the cable is called the nominal cross section...
as long as the resistance of the conctor inside reaches the corresponding standard requirements, it can be judged as qualified...
it does not mean the cross section calculated according to the measured size of the conctor

9. If you know the specification and model, there must be its nominal sectional area in the model. This is the most basic parameter
if you don't know, peel off the cable head, measure the diameter of one strand of cable core with a caliper, calculate its circular area, and then multiply by the number of strands of cable core to get the cross-sectional area of cable
in general, the cross-section in the proct catalogue and manual is the nominal cross-sectional area, and the values are rounded to facilitate marking, without affecting the calculation and application in engineering.

10. A few square is a nominal value stipulated by the national standard, and a few square is the user's choice of wires and cables according to the load of wires and cables
the number of square wires is an oral term in the decoration of water and electricity construction. It is often said that the number of square wires does not add a unit, that is, square millimeter
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
generally speaking, the empirical power carrying capacity is about one kilowatt per square wire when the grid voltage is 220 v
copper wire can carry 1-1.5 kW per square meter, while aluminum wire can carry 0.6-1 kW per square meter. Therefore, an electric appliance with a power of 1 kW only needs one square of copper wire
when it comes to current, copper wire can carry 3a to 5A current per square meter in short distance transmission. If the heat dissipation condition is good, 5A / mm ~ 2, but not 3A / mm ~ 2
conversion method:
know the square of the wire, and calculate the radius of the wire with the formula of circular area:
square number of wire (square millimeter) = circumference (3.14) × The square of wire radius (mm)
the square of wire is known, so is the calculation of wire diameter, for example:
2.5 square the wire diameter of wire is: 2.5 ÷
3.14
=
0.8, and then square to get 0.9mm, so the line diameter of 2.5 square line is: 2 × 9 mm = 1.8 mm
if you know the diameter of the wire, the square of the wire can also be calculated by the formula of circular area:
square of the wire = circumference (3.14) × The square / 4 of the wire diameter
the cable size is also nominal by the square, and the multi strand wire is the sum of the cross-sectional areas of each wire

calculation formula of cable cross-sectional area:
0.7854
×
square of wire radius (mm)
×
number of strands
for example, 48 strands (wire radius 0.2 mm per strand) of 1.5 square wires:
0.7854
× 0.2
×< br />0.2 ×
48
=
1.5 square meters