The selection of cables, how to choose wires and cables

i=p (, the power factor is taken, if you really are a pure resistive load you can take 1, then the current is 182A. The current carrying capacity of the conventional 10mm2 copper core cable is 61A when it is laid directly in the ground at 30°, and it is enough to use 4 10 square cables at the same time, considering the protection of electrical appliances (the tripping current of the circuit breaker or fuse is set to 200A). If you select a single cable, you need to select a 3x95+1x50 cable.

I don't know how you use this 120kw, I think at least 3 120 + 70, preferably 3 150 + 75

But now they all use YJV.

1. Looking at the packaging, the wires of the national standard are often better, neat, and have a sense of quality when you hold them.

2. To open the package and take a look at the wires inside, the wire square requirements of the national standard are skin thickness (insulation thickness), too thick is non-standard, and the corresponding inner core is definitely not enough.

3. Burn it with fire and extinguish it within 5s after leaving, and it has a certain flame retardant function for the national standard line.

4. Look at the inner core, the higher the brightness of the inner core (copper), the better the copper, and the luminosity is uniform, shiny, and there is no sense of hierarchy. The national standard requires that the inner core must be made of oxygen-free copper. Non-standard such as black rod copper, there may be potential accidents.

5. The thickness of the inner core has certain requirements in the country, but it is not very strict. But there are not many mistakes, just a small point, and the error is generally not visible with the eye.

6. Length, the state does not force the rice, but there are many manufacturers who also beat the rice, and the rice is not necessarily the national standard, but the general national standard generally does not beat the rice. Non-standard rice is just a means.

7. The state stipulates that there must be a certain logo on the wire, and the maximum will not exceed 500mm, and the next same logo will be played, and there are generally product trademarks, manufacturer names, implementation standards, etc.

There are the following types of insulated wires: PVC insulated wires, PVC insulated wires, nitrile PVC mixture insulated wires, rubber insulated wires, agricultural underground directly buried aluminum core plastic insulated wires, rubber insulated cotton yarn textile wires, PVC insulated nylon sheathed wires, PVC insulated soft wires for electricity and lighting, etc. Select according to the usage environment.

1. The selection of power cables should follow the following principles:

1) The rated voltage of the cable should be greater than or equal to the rated voltage of the power supply system at the installation point;

2) The continuous allowable current of the cable shall be equal to or greater than the maximum continuous current of the power supply load;

3) The cross-section of the wire core should meet the requirements of the stability of the power supply system when it is short-circuited;

4) Check whether the voltage drop meets the requirements according to the cable length;

5) The minimum short-circuit current at the end of the line should enable the protective device to operate reliably.

Cable ampacity estimation formula:

Multiply by nine at 2.5 and subtract one by one straight up.

Thirty-five times 3.5, double in a group minus five.

The conditions have been changed and converted, and the high-temperature nine-fold copper has been upgraded.

The number of pipe roots is two, three, four, eight, seven and six folds full of load current.

1. Look at the brand: brand ranking and value are the cornerstone of product quality and safety, and choosing a regular and well-known brand can avoid buying inferior products to a large extent. For example, as one of the top 500 Asian brands, one of the top 500 Chinese enterprises, and an enterprise with a brand value of 100 million yuan, Far Eastern Group has been operating with ingenuity for 38 years and has won the "National Quality Award" and has a good reputation.

2. Look at the product:

Packing: neat disc shape, good packaging, complete items on the certificate, including but not limited to trademark, factory name, factory address, **, specifications, cross-section, inspectors, etc.;

Inner core: choose copper material core with longer service life and safer, pure copper core is preferred, and the color is purple-red; In addition, it is also necessary to see whether the inner core is in the middle of the insulation wrap. Inferior wire rods have a large degree of eccentricity problems.

The eccentricity rate is high, and the thin part is easy to be broken down, which has the risk of causing a short circuit and causing fire;

Smoke: Burn the wires with a lighter, ordinary wires will release toxic gases when they encounter an open flame, which will further increase the risk of short circuits and fires. When the flame retardant wire encounters an open flame, it will break off from the fire, and no toxic gas will be generated.

Therefore, it is more recommended that you install and use low-smoke halogen-free flame retardant wires, which are safer and more environmentally friendly;

Weight: The length of the national standard line, the general number of packages is marked as 100m, and the actual measurement is also full of meters and copper, with a certain weight.

The property right of general residential housing is 70 years, and the Far Eastern's "good core and high safety and environmental protection wire" can be used for 70 years, truly achieving a wiring and lifelong worry-free. In terms of appearance, the Far Eastern Group's "good series" wires are beautifully packaged, and the product certification information is complete; The raw material of the inner core is pure copper core, which has low resistivity, strong conductivity, energy saving and power saving, and achieves low eccentricity, high concentricity, anti-breakdown, and safer electricity consumption. The insulation layer is made of high-quality environmentally friendly PVC material insulation layer, which is more wear-resistant, corrosion-resistant, and age-resistant, and at the same time adds flame retardant, which has the characteristics of high-performance flame retardant, low smoke and halogen-free, non-toxic and harmless; The length of the national standard line standard is marked with 100 meters, and the actual length is 95-100 meters, and the Far East can ensure the length of 100 meters in this regard, which is better than the national standard, 3. Look at the strength, whether there are any buildings we are familiar with in the decoration of these materials, the choice of the Far East is the common choice with the Hong Kong-Zhuhai-Macao Bridge, China Zun and so on.

4. Looking at after-sales, one of the important factors that distinguish big brand wires from miscellaneous brands on the market is that there is a first-class guarantee that can be traced back to the whole process, which can effectively prevent consumers from buying counterfeit wires. Far Eastern Wire has a double after-sales guarantee, not only Pacific Insurance underwrites, 30 days no reason to return and exchange, each coil of wire packaging also has *** anti-counterfeiting protection, full traceability, peace of mind.

First of all, it is necessary to calculate the total power of electrical equipment;

The current is then calculated from the power, which is the current carrying capacity;

Finally, according to the current carrying capacity, the size of the cable is determined.

For example: a motor with a total power of 50kw, when converted into a current of 100A, that is, the current carrying capacity of 100A, 100A needs at least 25 square cables, considering that some cables are not national standards, so at least a larger cable is used, that is, 35 square meters!

After reading the examples, you will definitely ask, how to convert power into current, and how to determine the cable specification of current. This problem varies depending on the temperature, material, and electrical equipment.

I can say the simplest rough way to memorize, which is 1kw for 2a, five amps per square.

It is recommended to choose a lot of copper wires with very thin cross-sections wound into a strand, because the current has the effect of skin accumulation, so that the current carrying capacity of the thin copper wire is larger with the same cross-section.

It is selected according to the size of the current and the installation method of the cable.

The principle of cable selection is [simple algorithm]:

For wires below 10mm2 (including 10mm2), multiply the cross-sectional area of the wire by 5 is the current carrying capacity of the cross-sectional wire.

The corresponding cross-sectional area of 100mm2 or more is multiplied by 2

16mm mm2 times 4

35mm mm2 times 3

70mm mm2 multiplied.

If the wire is multiplied by the coefficient of the pipe, the total cross-sectional area of the wire is not more than 40% of the cross-sectional area of the pipe) used in high-temperature places within the coefficient of Celsius).

The cross-sectional area of bare wire (such as overhead bare wire) is multiplied by the corresponding magnification and then multiplied by 2 (e.g., 16mm2 wire: 16*4*2).

The above is calculated based on the cross-sectional area of the aluminum wire.

Copper wire upgrade calculation means that the current carrying capacity of copper wire is equal to the current carrying capacity of aluminum wire, and so on.