Take you to understand cables, power cords

1. Preparation before production
1.1 Define the production tasks and lead the insulated cores of various specifications.
1.2 Change the pitch as required by the process card.
1.3 Clear the obstacles around the cable forming machine.
2. Operational requirements
2.1 The operator must be familiar with the outer diameter and structure size of the insulated cores of various specifications.
2.2 The cable must be flat and even during operation, and maintain a certain amount of tension to prevent the wire core from loosening and messing up and hanging off on the cable forming machine.
2.3 Install the wire reels of 2, 3 or 4 different colors on the power cord plug of the cable forming machine, and install the take-up reel on the shaft at the take-up position.
2.4 Put the cores of the cable together and pass them through the shaft hole of the cable machine.
2.5 When the cable is formed, the cable pitch should be checked before it is officially started for production.
2.6 After the cable is connected to the power cord, the insulation should be stripped off, and the conductor should be cut in half and wound tightly. The joint should not be larger than the outer diameter of the cable, and a mark should be made at the joint.

First, aluminum core cables should be used in general environments, copper core cables should be used in places with severe vibration and special requirements; copper core cables should be used in large-scale important public buildings.
Second, for buried cables, armored cables with outer sheaths should be used; in places where there is no possibility of mechanical damage, plastic sheathed cables or lead-clad cables with outer sheaths can also be used;
Third, in the soil where displacement may occur, (such as swamps, quicksands, large buildings) buried laying should use steel wire armored cables, and measures can also be taken to eliminate the stress on the cables due to cable displacement, such as prestressing Leave the cable length and use sheet piles or rows of piles to reinforce the soil.
Fourth, in the soil with chemical corrosion or stray current corrosion, it is not suitable to bury cables in the ground. If it is necessary to bury the ground, anti-corrosion cables should be used or measures to prevent stray currents from corroding the cables should be adopted.
Fifth, the cables laid in the pipe or the pipe should be plastic sheathed cables, or bare armored cables.
Sixth, when laying cables in cable trenches or cable tunnels, there should be no flammable and prolonged outer sheath, and bare armored cables, bare lead cables or flame-retardant plastic sheathed cables should be used.
Seventh, cables with outer sheath or all-plastic power should be used for overhead laying.
Eighth, when cables are laid in places with large height differences, plastic insulated cables, non-drip cables or dry insulated cables should be used.
Ninth, four-core cables should be used in three-phase four-wire lines.
Tenth, fire-resistant cables can be used for important backup trunk lines (such as the tie line between the backup generator set and the transformer).

1. External force violation

If wires and cables are laid in areas with particularly strong acid and alkali properties, they will usually be corroded. The thickness of the protective layer will be eroded by organic chemical or electrolytic methods for a long time, resulting in ineffective protective layer thickness and reduced insulation layer. It can also cause cable failure. Therefore, it is necessary to analyze the local soil quality before laying wires and cables.

2. Natural weather
When installing wires and cables, try to avoid being exposed to the sun or being damaged by strong winds and rain, because the accumulation of wires and cables over time will accelerate the embrittlement of the sheath and reduce the service life of the wires and cables.

3. Suitable temperature
The external natural environment and heat source where the cable is located will also cause the cable to have too high temperature and thermal breakdown of the insulation, so that it will explode and catch fire.

4. Overload operation
Wires and cables should not be overloaded. This is because of the thermal effect of the current. The load current will inevitably cause the electrical conductors to become hot. In addition, the skin effect of the charge, the eddy current loss of the steel armor, and the dielectric loss of the insulation layer will also cause additional damage. Heat, which in turn increases the temperature of the cable. During long-term overload operation, an excessively high temperature will accelerate the embrittlement of the insulating layer, resulting in thermal breakdown of the insulating layer.

Wires and cables are one of the core and most important elements of the current cable system. In our daily applications, we need to check and repair at any time, and take some defensive measures in advance, which can extend the service life of the wires and cables.

The power line carries current. Usually the method of current transmission is point-to-point transmission. Power cords can be divided into AC AC power cords according to their purpose. Click here to add a picture to illustrate DC DC power cords. Usually AC power cords are wires that pass high-voltage alternating currents. Such wires require uniform standards to obtain certification due to higher voltages. Can be officially produced. The DC line basically passes the low voltage direct current, so the safety requirements are not as strict as the AC line, but for safety reasons, countries still require unified safety certification.
How to choose the power cord first

1. Standard issues
First of all, you need to know which country your product is sold to, and different companies have different requirements on power cord standards. For example, if you go to European countries, the product needs to have EU VDE certification. If you go to the United States, you need to have the American UL certification. If you go to Australia, Japan, Italy and many other countries, there are relevant product certification requirements. Similarly, if this is not certain, you may not be able to use the product you have made, so this is the primary problem.

2. Power cord specifications and thick wires
The power cord is divided into two-core and three-core, depending on the type of electrical appliances. Also divided into specifications, such as national standard 52 lines (light PVC sheathed flexible cables) 53 lines (ordinary PVC sheathed flexible cables), VDE divided into H03VV-F, H05VV-F, etc. In addition, the power cord is also divided into thickness, such as: 0.5mm2 0.75mm2 1.0mm2 1.5mm2. The specifications and the thickness of the wire are mainly based on the power of the electrical appliance. For details, please refer to the relevant national standards.

3. The color of the power cord
This is mainly based on the color of the product. If your product is white, it should be equipped with a white power cord and a black power cord. It is always not pretty.

4. The length of the power cord
The length of the power cord should be determined according to the user's use. If it is too long or too short, it is inconvenient for the user to use it.

For twisted-pair cables, users are most concerned about several indicators that characterize their performance. These indicators include attenuation, near-end crosstalk, impedance characteristics, distributed capacitance, DC resistance, etc.
(1) Attenuation
Attenuation is a measure of signal loss along the link. The attenuation is related to the length of the cable. As the length increases, the signal attenuation also increases. The unit of attenuation is "db", which represents the ratio of the signal strength of the source transmitting end to the receiving end. Since the attenuation varies with frequency, the attenuation at all frequencies within the application range should be measured.
(2) Near-end crosstalk
Crosstalk is divided into near-end crosstalk and far-end crosstalk (FEXT). The tester mainly measures NEXT. Because of the line loss, the magnitude of FEXT has less influence. Near-end crosstalk (NEXT) loss is a measurement of signal coupling from one pair of wires to another pair of wires in a UTP link. For UTP links, NEXT is a key performance index, and it is also the most difficult index to accurately measure. As the signal frequency increases, its measurement difficulty will increase. NEXT does not mean the crosstalk value generated at the near end point, it just means the crosstalk value measured at the near end point. This value will vary with the length of the cable, the longer the cable, the smaller the value becomes. At the same time, the signal at the transmitting end will be attenuated, and the crosstalk to other wire pairs will be relatively small. Experiments have proved that only the NEXT measured within 40 meters is more real. If the other end is an information socket farther than 40 meters, then it will produce a certain degree of crosstalk, but the tester may not be able to measure this crosstalk value. Therefore, it is best to perform NEXT measurements at both endpoints. The tester is equipped with corresponding equipment so that the NEXT value at both ends can be measured at one end of the link
(3) DC resistance
TSB67 does not have this parameter. The DC loop resistance consumes part of the signal and converts it into heat. It refers to the sum of the resistance of a pair of wires. The DC resistance of the 11801 twisted pair must not be greater than 19.2 ohms. The difference between each pair should not be too large (less than 0.1 ohm), otherwise it means poor contact, and the connection point must be checked
(4) Characteristic impedance
Different from the loop DC resistance, the characteristic impedance includes resistance and the frequency of 1～100MHz inductance impedance and capacitance impedance, which is related to the distance between a pair of wires and the electrical properties of the insulator. Various cables have different characteristic impedances, and twisted-pair cables have 100 ohms, 120 ohms and 150 ohms.
(5) Attenuation crosstalk ratio (ACR)
In some frequency ranges, the proportional relationship between crosstalk and attenuation is another important parameter reflecting cable performance. ACR is sometimes expressed in terms of SNR (Signal-Noice ratio), which is calculated by the difference between the worst attenuation and the NEXT value. A higher value of ACR indicates stronger anti-interference ability. General system requirements are at least greater than 10 decibels
(6) Cable characteristics
The quality of the communication channel is described by its cable characteristics. SNR is a measure of the strength of the data signal taking into account the interference signal. If the SNR is too low, it will cause the receiver to be unable to distinguish between the data signal and the noise signal when the data signal is received, which will eventually cause data errors. Therefore, in order to limit the data error within a certain range, a minimum acceptable SNR must be defined.

1. The rubber power cord should be hung freely and fully twisted before use. The rubber power cord's reinforcing core should be fixed and bear the tension at the same time;
2. Multiple rubber power cords should be laid in rows. During operation, the rubber power cords move up and down along with the elevator. They move and bend frequently, requiring softness and good bending performance;
3. The rubber power cord is laid vertically and requires a certain tensile strength;
4. If there is oil pollution in the working environment, fire prevention is required, and the rubber power cord is required to not extend combustion;
5. Small outer diameter and light weight are required.
structure:
1. Use 0.2mm round copper single wire bundle to twist, wrap the isolation layer between the insulation and the conductor, and twist in the same direction when forming the cable to increase the flexibility and bending performance of the rubber power cord;
2. Add rubber power cord reinforcing core to the rubber power cord to withstand mechanical tension. The reinforcing core is made of nylon rope, steel wire rope and other materials to increase the tensile strength of the rubber power cord;
3. YTF type rubber power cord adopts neoprene as the main sheath to improve the weather resistance and non-flammability of the rubber power cord.

1. Load-bearing rubber power cord: the outer diameter is usually less than 12mm; the length is long, a single length of more than 3500m is supplied; oil and gas resistance, water pressure resistance 120MPa (1200 times atmospheric pressure); high temperature resistance: 100℃ or more; , Tensile strength: above 44KN; wear-resistant, resistant to hydrogen sulfide gas; all armored steel strands will not spread when they are broken, otherwise it will cause a waste well.
structure:
(1) The conductor has a flexible structure and is tin-plated;
(2) High temperature resistant polypropylene, ethylene-propylene rubber or fluoroplastics for insulation;
(3) Semi-conductive materials for shielding;
(4) High-strength galvanized steel wire for armor;
(5) Use special manufacturing technology.
2. Perforated rubber power cord: large hole cross-sectional area and tensile force, wear-resistant, vibrate, and not loose.
structure
(1) Medium flexible structure for conductor;
(2) Polypropylene, ethylene propylene rubber or other high temperature resistant materials for insulation;
(3) The size of conductor, insulation and armor is correct.
3. Rubber power cords for coal field, non-metal, metal, geothermal, hydrological, underwater, etc. surveys.
structure:
(1) Reinforced core and inner armor;
(2) The conductor is soft copper wire;
(3) Ordinary rubber for insulation;
(4) Sheath neoprene rubber;
(5) Metal or non-metal armor is used in special circumstances;
(6) Coaxial rubber power cables should be used for underwater rubber power cables;
(7) The comprehensive detector should have functions such as power and communication.
4. Rubber power cord of submersible pump: the outer diameter of the tubing is small, the outer size of the rubber power cord is required to be small; the depth of the well is increased, the power is large, the insulation is required to withstand high temperature, high pressure, and the structure is stable; good electrical performance, good insulation performance, and small leakage current; Long life, stable structure, reusability ability; good mechanical properties.
(1) For small and medium-sized oil pipes, use flat rubber power cords to ensure small dimensions; solid conductors with large cross-sections: stranded conductors, round rubber power cords;
(2) Use polyimide-fluoro46 sintered wire for rubber power cord core, ethylene propylene insulation; power rubber power cord uses ethylene propylene, crosslinked polyethylene heat-resistant insulation;
(3) Oil-resistant neoprene rubber, chlorosulfonated polyethylene and other oil-resistant and high-temperature resistant materials, lead sheath, etc.;
(4) Use chain armor;
(5) Halogen-proof structure, with a halogen-proof sheath added to the bare armor.

1. The universal rubber sheathed rubber power cord has a wide range of applications. It can be applied to all kinds of electrical equipment requiring mobile connections in general occasions, including electrical mobile equipment connections used in various sectors of industry and agriculture.
2. According to the size of the cross section of the rubber power cord and the ability to respond to mechanical external forces, it is divided into three types: light, medium and heavy. These three types of products have requirements for softness and flexibility, but the light-duty rubber power cords require high flexibility, and they must be light, small in size, and cannot withstand strong mechanical external forces; medium-sized rubber power cords have certain flexibility. And can withstand considerable external mechanical forces; heavy-duty rubber power cords have higher mechanical strength.
3. The rubber power cord sheath should be tight, strong and round. YQW, YZW, YCW type rubber power cords are suitable for field use (such as searchlights, agricultural electric plows, etc.), and should have good resistance to sunlight aging.
Structure
1. Conductive power cord: It is twisted with copper flexible wire bundle, and the structure is flexible. The large cross-section surface allows paper wrapping to improve the bending performance.
2. Natural styrene-butadiene rubber is used for insulation, with good insulation aging performance.
3. The rubber of outdoor products adopts neoprene or a mixed rubber formula based on neoprene.

1. Performance requirements for shielded power cords: basically the same as those for unshielded similar power cords.
2. Because it meets the requirements of equipment for shielding (anti-interference performance), it is generally recommended to be used in medium-level electromagnetic interference occasions; the plastic sheathed rubber power cord can be directly buried in the soil.
3. The shielding layer should be able to make good contact with the connecting device or one end is grounded, and the shielding layer should not be loosened, unthreaded, and not easily scratched by foreign objects.
1. Conductive power cord: tin plating is allowed in some occasions;
2. The surface coverage density of the shielding layer should meet the standard or meet the user's requirements; the shielding layer should be braided or wound with tinned copper wire; if an extruded sheath should be added to the shield, the shielding should be braided or wound with soft round copper wire.
3. In order to prevent the internal interference between cores or pairs, each core (or pair) can be produced separately for each phase shielding structure.

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