What is the maximum current and power that a 1mm2 power cord can pass? For example, for a wire of 2.5 square meters, how to calculate how much wire will be used in construction?

①For wires of 1.5, 2.5, 4, 6, and 10mm2, the cross-sectional area can be multiplied by 5 times.

②For wires of 16, 25mm2, the cross-sectional area can be multiplied by 4 times.

③For 35 and 50mm2 wires, the cross-sectional area can be multiplied by 3 times.

④For wires of 70 and 95mm2, the cross-sectional area can be multiplied by 2.5 times.

⑤For wires of 120, 150, and 185mm2, the cross-sectional area can be doubled.

The working temperature is 30℃, and the current carrying capacity under continuous 90% load for a long time is as follows:

1.5 square millimeters-18A

2.5 square millimeters-26A)

4 square millimeters-26A

6 square millimeters-47A

10 square millimeters-66A

16 square millimeters-92A

25 square millimeters-120A

35 square millimeters-150A

Power P=Voltage U×Current I=220V×18A=3960W

The wire load current value specified in the national standard GB4706.1-1992/1998 (part)

Copper core wire: Copper core wire cross-sectional area.. Allow long-term current

2.5 square millimeters (16A～25A)

4 square millimeters (25A～32A)

6 square millimeters (32A～40A)

Aluminum core wire: Aluminum core wire cross-sectional area.. Allow long-term current

2.5 square millimeters (13A～20A)

4 square millimeters (20A～25A)

6 square millimeters (25A～32A)

〖for example〗

1. Each computer consumes about 200 to 300W (about 1 to 1.5A), so 10 computers need a 2.5 square millimeter copper core wire for power supply, otherwise a fire may occur.

2. The power consumption of a large 3-hp air conditioner is about 3000W (about 14A), so one air conditioner needs a single 2.5 square millimeter copper core wire for power supply.

3. The incoming wires of houses are generally 4 square millimeters of copper wire. Therefore, the household appliances that are turned on at the same time must not exceed 25A (5500 watts). It is useless to replace the wires in the house with 6 square millimeters of copper wire. , Because the wire going into the meter is 4 square millimeters

4. In the early housing (15 years ago), the incoming wire was generally 2.5 square millimeters of aluminum wire. Therefore, the household appliances that were turned on at the same time should not exceed 13A (that is, 2800 watts).

5. Household appliances that consume a lot of power are: air conditioner 5A (1.2hp), electric water heater 10A, microwave oven 4A, rice cooker 4A, dishwasher 8A, washing machine with drying function 10A, electric water heater 4A caused by the power supply 90% of fires are caused by heat generated by the joints, so all joints must be welded, and contact devices that cannot be welded must be replaced within 5 to 10 years (such as sockets, air switches, etc.).

Long-term current allowed by national standard

4 square is 25-32A

6 square is 32-40A

In fact, these are theoretically safe values, and the limit values are even greater than these.

The maximum power allowed for the 2,5 square copper wire is: 5500W; 4 square 8000W, 6 square 9000W is no problem.

A 40A digital meter is absolutely no problem with a normal 9000W. The mechanical 12000W will not burn.

Copper core wire and cable current carrying capacity standard cable carrying capacity port decision:

Estimated formula:

Multiply two and five times by nine, and go up and down by one.

Thirty-five times three and five, both in groups minus five.

The conditions are changed and the conversion is added, and the high-temperature copper is upgraded with a 10% discount.

The number of piercing pipes is two, three, four, and eight or seventy-six percent is full of current.

Description:

The formula in this section does not directly indicate the current carrying capacity (safe current) of various insulated wires (rubber and plastic insulated wires), but is expressed by "cross section multiplied by a certain multiple", which is obtained through mental calculation.

"Two-and-a-half five times the number of times nine, and upwards minus one forward" refers to various cross-section aluminum core insulated wires of 2.5mm and below, and the current carrying capacity is about 9 times the number of cross-sections.

For example, 2.5mm' wire, the current carrying capacity is 2.5×9=22.5(A).

The multiple relationship between the current-carrying capacity of 4mm’ and above wires and the number of cross-sections is that the line number goes up, and the multiples are successively reduced by l, that is, 4×8, 6×7, 10×6, 16×5, 25×4.

"Fifteen times three point five, double pairs into groups minus five points", it is said that the carrying capacity of 35mm" wire is 3.5 times the number of cross-sections, that is, 35 × 3.5 = 122.5 (A).

For wires of 50mm’ and above, the multiple relationship between the current-carrying capacity and the number of cross-sections becomes a set of two wire numbers, and the multiples are successively reduced by 0.5. That is, the current-carrying capacity of 50 and 70mm' wires is 3 times the number of cross-sections; the current-carrying capacity of 95 and 120mm" wires is 2.5 times the number of cross-sectional areas, and so on.

"Conditions have changed, plus conversion, high temperature 10% copper upgrade." The above formula is determined by the aluminum core insulated wire and the open coating at an ambient temperature of 25°C.

If the aluminum core insulated wire is exposed to 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 calculation method, and then a 10% discount is enough; when the copper core insulated wire is not used, Its current-carrying capacity is slightly larger than that of the aluminum wire of the same specification. According to the above formula method, the current-carrying capacity of one wire number larger than that of the aluminum wire can be calculated. For example, the current carrying capacity of 16mm’ copper wire can be calculated as 25mm2 aluminum wire.

Calculate the current carrying capacity of the cable and select the cable (select the cable according to the current):

The current carrying capacity of the wire is related to the cross section of the wire, and also related to the material, model, laying method, and ambient temperature of the wire. There are many influencing factors and the calculation is more complicated. The current carrying capacity of various wires can usually be found in the manual. But using formulas and some simple mental arithmetic, it can be calculated directly without having to look up the table.

1. The formula is the relationship between the current-carrying capacity of the aluminum core insulated wire and the multiple of the cross section

10 under five, 100 on two,

25, 35, four and three realms

70, 95, twice and a half.

20% off for tube and temperature.

Add half of the bare wire.

The copper wire upgrade counts.

Explain that the ampacity (A) of various cross-sections is not directly pointed out by the formula, but expressed by multiplying the cross-section by a certain multiple.

To this end, the nominal cross-sections (square millimeters) of commonly used wires in my country are arranged as follows:

1, 1.5, 2.5, 4, 6, 10, 16, 25, 35, 50, 70, 95, 120, 150, 185...)

(1) The first sentence of the formula points out that the current carrying capacity (A) of the aluminum core insulated wire can be calculated as a multiple of the cross section.

The Arabic numerals in the formula indicate the cross-section of the wire (square millimeters), and the Chinese numerals indicate multiples. Arrange the cross-section and multiple relationship of the formula as follows:

1～10 16, 2535, 50 70, 95 120 or more

Five times four times three times two times half two times

Now it is clearer to compare with the formula, the formula "10 under five" means that the cross section is below 10, and the current carrying capacity is five times the value of the cross section. "100 on two" (read one hundred on two) means that the current-carrying capacity of a section above 100 is twice the value of the section. The cross-section of 25 and 35 is the boundary between four times and three times. This is the mantra "25, 35, Four and Three Realms". The cross-sections 70 and 95 are 2.5 times. From the above arrangement, it can be seen that, except for below 10 and above 100, the cross section of the conductor in the middle is a multiple of the same for each of the two specifications.

For example, the calculation of the current carrying capacity of the aluminum core insulated wire and the ambient temperature is not more than 25℃:

When the cross-section is 6 square millimeters, the calculated current-carrying capacity is 30 amps;

When the cross-section is 150 square millimeters, the calculated current carrying capacity is 300 amps;

When the cross-section is 70 square millimeters, the calculated current-carrying capacity is 175 amps;

It can also be seen from the above arrangement that the multiple decreases with the increase of the cross-section, and the error is slightly larger at the junction of multiple transitions. For example, cross section 25 and 35 are the boundary between quadruple and triple, 25 belongs to the quadruple range. According to the formula, it is 100A, but according to the manual, it is 97A. On the contrary, 35 is calculated as 105A according to the formula, but The look-up table is 117 amps. But this has little effect on usage. Of course, if you can "have a number in your chest", when selecting the wire cross section, it is more accurate to not let it be full of 100 amperes for the 25, and slightly more than 105 amperes for the 35. Similarly, the 2.5 square millimeter wire is located at the beginning of five times, which is actually more than five times (the maximum can reach more than 20 A), but in order to reduce the power loss in the wire, usually the current does not need to be so large. 12 Ann.

(2) The following three sentences are the handling of conditional changes.

"Through pipe, temperature, 80% or 10% discount" means: if it is laying through pipe (including laying of grooved board, that is, the wire is covered with a protective cover, and it is not exposed), after calculation, another 20% discount; if the ambient temperature exceeds 25℃, 10% off after calculation. If the temperature exceeds 25℃, it will be 20% off and then 10% off, or simply a 30% discount.

Regarding the ambient temperature, according to the regulations, it refers to the average maximum temperature of the hottest month in summer. In fact, the temperature fluctuates. Under normal circumstances, it does not affect the current carrying capacity of the wire very much. Therefore, discounts are only considered when the temperature exceeds 25°C in certain greenhouses or hotter areas.

For example, the calculation of download flow of aluminum core insulated wire under different conditions:

When the cross-section is 10 square millimeters through the pipe, the current-carrying capacity is 10×5×0.8=40A; if it is high temperature, the current-carrying capacity is 10×5×0.9=45A; if it is high temperature through the pipe, the current-carrying capacity is 10×5×0.7=35A.

(3) Regarding the current carrying capacity of bare aluminum wire, the formula points out that "bare wire plus half" means adding half after calculation. This means that the current carrying capacity can be increased by half of the bare aluminum wire of the same cross-section compared with the aluminum core insulated wire.

For example, calculation of current carrying capacity of bare aluminum wire:

When the cross-section is 16 square millimeters, the current-carrying capacity is 16×4×1.5=96 amperes, and if it is at high temperature, the current-carrying capacity is 16×4×1.5×0.9=86.4 amperes.

(4) For the current carrying capacity of copper wires, the formula points out "Copper wire upgrade calculation", that is, the order of the cross-section of the copper wires is increased by one level, and then calculated according to the corresponding aluminum wire conditions.

For example, the ambient temperature of a bare copper wire with a section of 35 square millimeters is 25°C, and the current carrying capacity is calculated as follows: 50×3×1.5=225A by upgrading to a bare aluminum wire of 50 square millimeters.

For cables, there is no introduction in the formula. Generally, for high-voltage cables directly buried in the ground, the relevant multiples in the first sentence can be directly used for calculation. For example, the current carrying capacity of a 35 square millimeter high-voltage armored aluminum core cable buried in the ground is 35×3=105A. The size of 95 square millimeters is about 95×2.5≈238A.

The cross section of the zero line in the three-phase four-wire system is usually selected to be about 1/2 of the cross section of the phase line. Of course, it should not be less than the minimum section allowed by the mechanical strength requirements. In a single-phase line, since the load current passed by the neutral line and the phase line are the same, the cross section of the neutral line should be the same as the cross section of the phase line.