Plan the wiring layout
Functional zoning: partition according to different functional modules in the PLC control cabinet, such as power module, CPU module, I/O module, etc. Place components with similar functions in the same area, such as all relays in one area and all signal conditioning modules in adjacent areas, so that the wiring can be more regular.
Consider heat dissipation: For components with high heat generation, such as high-power power supplies, inverters, etc., sufficient space should be reserved to ensure smooth air circulation and avoid heat accumulation. Generally speaking, there should be at least 5-10 cm of space around these components for heat dissipation.
Convenient maintenance and repair: When wiring, subsequent maintenance and repair work should be considered. Put components that need to be frequently operated or checked, such as fuses, switches, etc., in easy-to-reach locations. At the same time, the lines should be arranged in an orderly manner for easy identification and troubleshooting.
Choose the right wires and cables
Select according to current and voltage: Select wires and cables according to the actual current and voltage in the circuit. Generally speaking, the rated current of the wire should be greater than 1.5-2 times the actual working current. For higher voltage lines, choose cables with appropriate withstand voltage levels. For example, for a 380V power circuit, a cable with a withstand voltage level of 500V or above should be selected.
Consider signal type: Use different cables for digital and analog signals. Analog signal cables should have good shielding performance to reduce electromagnetic interference, such as shielded twisted pair cables; digital signal cables can use ordinary twisted pair cables, but for high-speed digital signals, cables with characteristic impedance matching may be required.
Flexibility and mechanical strength: For parts that need to be moved or bent frequently, use wires and cables with good flexibility. For places that may be subject to mechanical external forces, such as the edge of the cable tray, choose cables with a certain mechanical strength, or provide additional protection for the cables.
Follow wiring principles
Separate strong and weak currents: Strong current lines (such as power circuits) and weak current lines (such as sensor signals and communication lines) should be wired separately to avoid electromagnetic interference from strong currents to weak currents. The distance between strong and weak current cables should generally be kept at more than 30-50 cm. If space is limited, at least metal partitions should be used for isolation.
Parallel wiring and cross wiring: Try to minimize the length of parallel wiring, because parallel wiring is prone to electromagnetic coupling interference. If parallel wiring is necessary, shielding measures should be taken. When the lines need to cross, it is best to cross at right angles to reduce mutual electromagnetic interference.
Clear line direction: The direction of wires and cables should be neat and clear to avoid chaos. Generally, wiring is carried out in the order from power supply to load and from PLC module input to output, so that the signal flow is clear at a glance.
Use appropriate wiring accessories and techniques
Use cable troughs and cable ties: Cable troughs can neatly store wires and cables to prevent the lines from being exposed. When placing wires and cables into cable troughs, be careful not to squeeze them too much to avoid damaging the cables. Cable ties are used to tie cables to make the cable bundle more compact, but the cable ties should not be tied too tightly to avoid affecting the service life of the cables.
Clear identification: Each wire and cable, each terminal and each component must be clearly identified. Labels can be printed using a label printer. The label content should include information such as line number, signal name, starting point and end point, so that the line can be quickly and accurately identified during maintenance and troubleshooting.
Good grounding: Proper grounding is very important. The grounding resistance of the PLC control cabinet is generally required to be less than 4 ohms. All components that need to be grounded, such as the shielding layer of the shielded cable, equipment with a metal shell, etc., must be connected to the ground bus to ensure the reliability of the grounding.
