Wires and cables used to transmit power and signals are used in a wide variety of applications and locations. In order to avoid troubles and accidents, it is very important to consider the place of use and purpose when selecting a model. Here, the basics of using wires and cables and what to consider when selecting them will be introduced.
How to use wires/cables
1) Use of reels/reels
1. The coil should be stored in an indoor flat place, and should be lifted as much as possible for transportation instead of rolling.
2. The reel cannot be placed flat, otherwise the coil wound on it will be misaligned and cannot be pulled out.
3. Do not roll the reel. When you have to roll the reel, you must pay attention to the direction in which the reel is rolled (rolled in the direction that the cable will not loosen). If you turn it in the opposite direction, the cable will come loose and it will be difficult to pull it out.
4. When stacking coils and reels, they must be strictly prevented from falling. Excessive shock to wires and cables can cause significant performance degradation. Especially when handling vinyl wire in cold regions, care must be taken as it is prone to breakage.
2) Precautions for wiring construction
1. Cobblestones, protrusions, concrete frames and other obstructions must be thoroughly removed when wiring. In addition, at the construction site, sufficient attention must be paid to the impact caused by falling foreign objects, and the nails on the footboards and wooden boxes can easily cause trauma.
2. When wiring the wire wound on the reel, the wire may be stretched or loosened in the length direction due to the repeated tension change, and the wire may pop out or bend near the winding start opening. In order to suppress the bending of the electric wire, it is necessary to remove the end of the electric wire at the start of winding the reel, and it is necessary to perform work while being careful that the electric wire protrudes from the winding start port. Be especially careful with long, thin cables.
3. When wiring, it is necessary to use rollers etc. to prevent excessive tension on the wires. The allowable tension during wiring work is shown in Table 1 below.
Table 1. Allowable Tension
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Wiring Supplies
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Conductor type
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allowable tension
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pull tab
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copper
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68.6MPa (7kgf/mm2) × (number of cable cores) × (conductor cross-sectional area mm2) or less
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aluminum
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39.2MPa (4kgf/mm2) × (number of cable cores) × (conductor cross-sectional area mm2) or less
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Metal mesh
(cable net sleeve)
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copper, aluminum
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Vinyl and polyethylene mesh sleeves are 10MPa (1.02kgf/mm2) × (cross-sectional area of mesh sleeves * mm2) However, the allowable tension of the conductor must not be exceeded.
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Notes
Note 1) When three single-core cables are inserted into hole I during pipeline laying, etc., the number of cable cores is calculated as 2 cores.
Note 2) When using a wire mesh to pull out the cable for wiring, it is necessary to cover the cable with a wire mesh of 500mm or more, and bundle the ends of the wire mesh to ensure that the mesh sleeve is evenly stressed.
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*Calculation formula S = πt (D – t)
S: the cross-sectional area of the net sleeve (mm2)
t: thickness of net sleeve (mm)
D: Machining outer diameter (mm)
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4. Rubber and plastic cable wires are somewhat flexible compared to paper and lead-coated cables, but their electrical performance will degrade if they are extremely bent. When wiring, care must be taken not to bend less than the values shown in Table 2 below.
Table 2. Allowable bending radius of rubber-plastic cable
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Kind of cable
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single core
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Multi-core
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Remark
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undivided conductor
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split conductor
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Unshielded
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8D
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12D
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6D
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with shielding
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10D
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12D
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8D
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Armoured cable with steel tape
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three cores
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–
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–
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6D
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(8D)
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( ) are high-voltage cables
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Corrugated Steel Pipe Armor
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–
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–
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8D
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Lead shield/wire armor
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10D
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12D
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10D
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smooth aluminum
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20D
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20D
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20D
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Corrugated Aluminum
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15D
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15D
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15D
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*For mobile
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6D
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–
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4D
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Unshielded
low voltage rubber cable |
Notes
※This value does not apply to reel-wound, curtain-type cables, etc. that can be repeatedly bent at a fixed position all the time.
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D: The outer diameter of the cable (mm), but the three-core cable is the diameter of the circumscribed circle (mm)
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5. If the root of the cable has a bend, the force that presses the cable against the bend will work when the cable is pulled out of the routing. This force is called side pressure, if the side pressure is too high, the cable performance will be degraded, so you need to ensure that the side pressure is lower than the following values when wiring.
· Round cable: 300kg/m
· Three-core cable: 250kg/m
· Communication cable: In principle, it should be 0kg (conditions need to be confirmed with the designer)
(refer to)
The cable side pressure (P) is calculated as P (kg/m) = tension (kg) / bending radius (m).
Table 3. Allowable bending radius of communication cables
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Cable classification
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Bending radius when connecting and supporting |
Bend radius when laying
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PE (PVC) sheathed cable (unshielded)
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4D and above
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10D and above
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Braided shielded cable
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4D 〃
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10D 〃
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Laminated Jacketed Cable
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6D 〃
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15D 〃
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Lead shielded cable
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6D 〃
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15D 〃
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Bellows Sheathed Cable
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6D 〃
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15D 〃
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Aluminum sheathed cable
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8D 〃
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20D 〃
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Wire Armored Cable
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8D 〃
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20D 〃
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Steel Tape Armored Cable
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8D 〃
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20D 〃
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Notes
Note: Generally speaking, the allowable bending radius of shielding tape is smaller when it is wound horizontally than when it is wound vertically. Comparing corrugated (corrugated tube) with flat, the corrugated type can be slightly smaller.
Table 4. Coaxial Cable Allowable Bend Radius
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Cable classification
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Bending radius when connecting and supporting
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Bend radius when laying
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The outer conductor is braided
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4D and above
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10D and above
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Outer conductor braid + plastic tape with metal foil
(Example: FB, FB-LITE, SFA-LITE, HQ/SUPER) |
6D 〃
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15D 〃
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6. Polyethylene insulators other than black may crack (ultraviolet degradation) in direct sunlight for several months, so the specified protective tape needs to be wrapped around the low voltage cable insulator.
7. Moisture in cable conductors can significantly reduce cable life. Especially when pulling into underground pipelines or pipes where there is water, it is necessary to completely seal the end part. If the cable is cut and placed, immediately waterproof the cut end with self-adhesive tape or the like.
8. It is necessary to avoid laying the single-core cable in the ventilation pipe with steel reinforcement or fixing the cable with steel tape, so as to avoid the deterioration of the cable due to the temperature rise of the iron piece.
Things to Consider When Sizing Wire/Cable
(1) Use temperature conditions
The degree of cold resistance and heat resistance is considered according to whether the use temperature is normal temperature, low temperature or high temperature.
Table 5. Cable Selection
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Use ambient temperature
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-15℃～60℃ ordinary PVC sheath
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-15℃～75℃ Heat-resistant PVC sheath
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-30℃～60℃ Cold-resistant PVC sheath
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-50℃～75℃ PE sheath
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(2) Use environment
Consider the degree of chemical resistance, oil resistance, water resistance, pressure resistance, gas resistance, flame resistance, and explosion resistance.
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When coming into contact with chemicals
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METASEAL cable, MAZE cable
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flame retardancy
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Flame Retardant: Flame Retardant PVC Sheath
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Flame Retardant/Low Hydrochloric Acid: Flame Retardant Low Hydrochloric Acid PVC Sheath
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High flame retardant halogen-free: flame retardant environmental protection cable
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Type of flame retardancy
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①High flame retardant
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② Flame retardant
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③Non flame retardant
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Corresponding cable case
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· Flame retardant PVC sheathed cable
(F-CV, etc.) · Flame retardant halogen-free sheathed cable / halogen-free flame retardant PE sheathed cable
(NH-CE, etc.) · High flame retardant halogen-free fire-resistant cable
(NH-FP) · High flame retardant halogen-free heat-resistant cable
(NH-HP) |
· General PVC sheathed cable
(CV, etc.) · Flame-resistant PE sheathed cable
(flame-resistant CE, etc.) · Environmental protection cable
(EM CE/F, etc.) · Fire resistant cable
(EM-FP) · Heat resistant cable
(HP) (EM-HP) · Communication cable
(FCPEV) |
· General PE sheathed cable (CE, etc.)
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Examples of required properties
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Vertical Tray Burning Test
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tilt test
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–
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Specification example
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JIS C 3521-1986
(IEEE Std. 383-1974) |
JIS C 3005-2000
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–
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Flame retardancy order
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① ＞ ② ＞ ③
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(3) Wiring (laying) method
Consider the appropriateness of wiring (laying) and methods such as equipment internal wiring, equipment outlet wiring, indoor wiring, overhead lines, direct burial, and suspended wiring.
(4) How to use
Consider whether it is for stationary use or mobile use, whether there is bending or twisting, and check whether the movement, degree, frequency and duration of bending and twisting are appropriate.
Consider the degree, frequency and duration of external forces such as vibration, shock, expansion, compression, tension, etc.
Consider the degree, frequency and duration of external forces such as vibration, shock, expansion, compression, tension, etc.
(5) Restrictions on construction methods
Consider the conditions of transportation, scaffolding, power supply, fire, tools, construction period, engineering, etc., and consider the proficiency of operators, the availability of connections, end processing, and the degree of difficulty, and discuss the usability of wires.
(6) Voltage
Consider the circuit voltage, voltage fluctuation, abnormal voltage, AC/DC, etc. to determine the rated voltage (nominal voltage) of the cable.
(7) Current and voltage drop
Determine the conductor size according to normal current, accident current, load factor, overload degree, allowable voltage drop, service conditions and allowable current. In this case, consider whether to use multiple single-conductor cables or multi-conductor cables.
(8) Number of cores
Consider the allowable current, inductance, wire thickness, terminal board, presence or absence of connections, connectors, etc. to determine the number of cores.
(9) Circuit and circuit composition
Determine the degree of insulation resistance, high-frequency characteristics, and transmission characteristics according to the necessity of the circuit and circuit mode, and then select the insulation material and wire structure accordingly.
(10) Inductance, crosstalk
The shielding (electrostatic, electromagnetic) method should be determined according to the required degree and the degree of the grounding system, and the best shielding structure (tape shielding, braided shielding, aluminum shielding layer, etc.) should be selected.
(11) Regulations
Discuss regulatory limitations.
(12) Economical
