The production of PLC control cabinets involves standards in many aspects, including design, electrical component selection, cabinet manufacturing, wiring, etc. The following are some of the main production standards:
Design standards
Functional design
According to the actual control needs, the electrical schematic diagram should be accurately drawn to ensure that the connection and signal transmission of PLC and related equipment conform to the process flow and control logic, and meet the automation control requirements of the production process.
Reasonably plan the I/O point allocation of PLC, and reserve a certain margin to cope with possible subsequent functional expansion or modification.
Safety design
Follow relevant safety standards, such as setting emergency stop buttons, safety door locks, etc., to ensure that the power supply can be quickly cut off in an emergency to ensure the safety of personnel and equipment.
For possible overcurrent, overvoltage, undervoltage, leakage and other faults, design corresponding protection circuits, such as fuses, thermal relays, leakage protectors, etc.
Maintainability design
The layout of the control cabinet should be easy to operate and maintain, and the electrical components should be kept at an appropriate distance to facilitate installation, commissioning and maintenance by maintenance personnel.
Design a clear identification and labeling system, and clearly mark each electrical component, terminal block, wire duct, etc. to facilitate quick identification and fault finding.
Electrical component selection standards
PLC selection
Select a PLC of appropriate model and specification according to the complexity of the control task, I/O points, storage capacity, computing speed and other requirements.
Consider the reliability, anti-interference ability, environmental adaptability and other factors of the PLC to ensure that it can operate stably in harsh industrial environments.
Other component selection
Low-voltage electrical components such as contactors, relays, and circuit breakers should be selected according to parameters such as load type, rated current, and rated voltage to ensure that they can reliably connect and disconnect the circuit.
Select a suitable power module to ensure that its output voltage and current are stable and can meet the power supply requirements of PLC and other electrical components.
Cabinet manufacturing standards
Cabinet material and structure
The cabinet is generally made of high-quality cold-rolled steel or stainless steel plates, with sufficient strength and rigidity to effectively protect the internal electrical components.
The cabinet structure should comply with relevant standards, such as IP protection level requirements. Generally, the IP protection level of control cabinets used indoors shall not be less than IP30, and that used outdoors or in harsh environments shall not be less than IP54.
Cabinet size and layout
According to the number and size of electrical components, the size of the cabinet should be reasonably designed to ensure sufficient internal space and neat and beautiful installation of electrical components.
The cabinet should be divided into different functional areas, such as power supply area, PLC installation area, relay area, terminal strip area, etc., and a certain distance should be maintained between each area to facilitate wiring and maintenance.
Wiring standards
Wiring method
Generally, wire trough wiring or cable tray wiring is adopted. Wire troughs and cable trays should have sufficient capacity to ensure neat and orderly wiring, and facilitate maintenance and replacement.
Different types of wires and cables should be wired separately, such as power lines and signal lines, weak current and strong current, etc., to avoid mutual interference.
Wire and cable selection
According to the rated current, voltage drop and other requirements of electrical components, select wires and cables of appropriate specifications to ensure that their current carrying capacity meets the requirements and the voltage drop is within the allowable range.
For signal transmission lines, cables with appropriate shielding performance, such as shielded twisted pair cables, coaxial cables, etc., should be selected according to the signal type and transmission distance to improve the reliability of signal transmission.
Wiring process
Wires and cables should be laid horizontally and vertically, arranged neatly, avoiding crossing and overlapping, and fixed firmly with wire clips or cable ties.
Clear and firm identification plates should be installed at both ends of wires and cables, indicating information such as line number, starting point, and end point, for easy inspection and maintenance.
