Online Consultation The processing quality of electrical control cabinets (electrical cabinets) directly affects the stability, safety, and service life of electrical equipment, involving multiple requirements such as structural strength, electrical compatibility, and protective performance. The following provides a detailed explanation of key considerations during the manufacturing process from five dimensions: material selection, structural processing, electrical layout, process details, and safety regulations:
1、 Material and board selection
1. Material requirements
Main framework:
Priority should be given to cold-rolled steel plates (SPCC) with a thickness of ≥ 1.5mm (load-bearing parts ≥ 2.0mm), surface galvanized or spray treated, and anti-corrosion performance must pass salt spray testing (no rust for ≥ 48 hours).
The outdoor cabinet can be made of stainless steel (304/316) with a thickness of ≥ 2.0mm. During welding, argon arc welding should be used to avoid intergranular corrosion.
Insulation components:
The partitions, cable trays, etc. are made of epoxy resin boards or ABS engineering plastics, with an insulation resistance of ≥ 10M Ω and a flame retardant rating of UL94-V0.
2. Pre treatment of sheet metal
Before cutting:
Check the flatness of the board (warpage ≤ 1.5mm/m), ensure that there are no scratches or rust on the surface, and perform deburring treatment (polishing the edges to R0.5~R1.0mm) to prevent cutting operators or damaging the wiring harness.
Surface Treatment
Before welding, rust and oil should be removed (wiped with alcohol or acetone), and phosphating treatment (film thickness 1-3 μ m) should be carried out before spraying to ensure coating adhesion (no peeling detected by cross cutting method).
2、 Key points of structural processing
1. Frame welding and strength
Welding process:
Carbon dioxide gas shielded welding (CO2 welding) or argon arc welding is used, with a current of 80-120A (thin plate ≤ 80A), and a weld leg height of ≥ 70% of the plate thickness (such as 2mm plate weld leg ≥ 1.4mm).
The load-bearing beams (such as the base and lifting ears) need to be fully welded, while other parts can be welded in sections (with an interval of 50-100mm and a weld length of 20-30 mm) to reduce deformation.
Post weld treatment:
Polish the weld seam until it is smooth (roughness Ra ≤ 12.5 μ m), check the diagonal difference of the frame ≤ 2mm (when the size is>1000mm), and use a right angle ruler to check the verticality (deviation ≤ 1.5 °).
2. Bending and drilling accuracy
Bending control:
The bending angle of the door panel and side panel is 90 ° ± 1.5 °, and the rebound compensation needs to be adjusted according to the material (such as stainless steel rebound angle of 5 °~8 °, mold angle set to 82 °~85 °).
The installation holes (such as guide rails and circuit breaker installation holes) are made using CNC punching machines or laser cutting, with a positional tolerance of ± 0.3mm and a hole diameter tolerance of ± 0.2mm (such as measuring 9.8-10.2mm for a diameter of 10mm).
Ventilation hole design:
The heat dissipation holes should be arranged evenly, using a louver structure (inclined angle of 60 °) or a combination of dust screen and fan. The opening area should be ≥ 0.5% of the cabinet volume, while avoiding direct blowing of electrical components.
3. Sealing and protection design
Sealing strip installation:
The door frame needs to be processed with a sealing groove (width ≥ 8mm, depth ≥ 5mm), embedded with EPDM rubber sealing strip, and compressed by ≥ 3mm when closed to ensure a protection level of IP54 (dust and water spray prevention) or higher.
Processing of inlet and outlet holes:
Rubber wire protectors should be installed at the cable entrance, with a hole diameter 2-3mm larger than the cable diameter and rounded edges (R ≥ 2mm) to prevent wear on the cable insulation layer.
3、 Electrical layout and process details
1. Component installation specifications
Space planning:
Arrange from top to bottom: instruments/indicator lights → control components (relays, PLCs) → power modules → circuit breakers/contactors → terminal blocks, with a spacing of ≥ 50mm for heat dissipation and maintenance.
Heating components (such as frequency converters and transformers) need to be installed separately in the heat dissipation chamber, with a distance of ≥ 100mm from other components. If necessary, forced air cooling (wind speed ≥ 2m/s) should be configured.
Installation and fixation:
The components need to be fixed with galvanized screws and spring washers, with a torque that meets the requirements (M4 screws have a torque of 1.2-1.5N · m, M5 screws have a torque of 2.0-2.5N · m), to avoid loosening or slipping.
2. Wire harness processing and wiring
Wire selection:
The power line adopts copper core flame-retardant cable (ZR-BVR) with a cross-sectional area of ≥ 2.5mm ² (current ≤ 16A), and the control line uses RVVP shielded wire (cross-sectional area ≥ 0.75mm ²) with anti-interference ability of ≥ 30dB.
Color differentiation: yellow/green/red for phase lines (L1/L2/L3), blue for neutral lines (N), yellow and green for ground lines (PE), black or white for control lines.
Wiring process:
The wiring harness needs to be fixed with nylon zip ties (with a spacing of 100-150mm), and it is forbidden to directly tie it to the component terminals;
When passing through metal holes, add protective wire sleeves with a bending radius of ≥ 6 times the outer diameter of the wire to avoid excessive bending and wire breakage.
3. Grounding and anti-interference
Grounding system:
The cabinet should be equipped with an independent grounding terminal (PE), connected to the ground with a yellow green wire of ≥ 4mm ², and the grounding resistance should be ≤ 4 Ω;
The metal casing, guide rail, and mounting plate of the components must be reliably connected to the grounding terminal of the cabinet (cross resistance ≤ 0.1 Ω).
Electromagnetic compatibility (EMC):
Separate the wiring of strong and weak electrical lines (with a spacing of ≥ 300mm), and when crossing is unavoidable, vertical crossing is required. Sensitive components (such as PLCs) need to be equipped with metal shielding covers.
4、 Safety and protection requirements
1. Anti electric shock design
Electrical clearance and creepage distance:
The air gap between phase lines is ≥ 10mm (working voltage ≤ 380V), and the creepage distance is ≥ 12.5mm (pollution level 2);
Exposed live parts (such as copper bars) need to be equipped with insulation sheaths, with a distance of ≥ 20mm from the cabinet shell.
Warning signs:
Post electrical schematics and safety warning labels (such as "High Voltage Danger" and "No Live Operation") on the inside of the cabinet door, with a font height of ≥ 3mm and clear visibility.
2. Mechanical safety
Edge processing:
All exposed edges of the cabinet should be blunt (R ≥ 1mm), and movable parts such as door shafts and hinges should have no sharp edges to prevent scratches by operators.
Protection level test:
After processing, conduct IP protection testing (such as water spray test, dust prevention test) to ensure that the cabinet works normally in humid and dusty environments.
5、 Process inspection and debugging
1. Inspection during the processing stage
First article inspection:
After welding the frame, check the diagonal difference and perpendicularity, and quickly verify the opening position of the door panel with a measuring tool (such as a hole position template). After confirming that there are no errors, mass production can be carried out.
Functional testing:
Perform power on test after installing components:
Insulation resistance test: Use a 500V megohmmeter to measure the phase to phase and ground resistance. A resistance of ≥ 2M Ω is considered qualified;
Voltage withstand test: Apply 1500V AC voltage for 1 minute without breakdown or flashover.
2. Packaging and transportation protection
Shock resistant packaging:
The components inside the cabinet are fixed with foam plates, the cabinet door is wrapped with pearl cotton after closing, and the external part is sealed with wooden boxes, and the bottom is equipped with shock pads (impact acceleration ≤ 15g).
Transportation identification:
The box is labeled with signs such as "Fragile, Do Not Press" and "Upward". During transportation, avoid tilting at an angle greater than 15 ° to prevent component displacement or detachment.
summary
The processing of electrical control cabinets should focus on safety, reliability, and ease of maintenance, with detailed control throughout the entire process from materials to processes. The structure should ensure strength and protection, the electrical layout should follow EMC specifications, and the process should strictly follow welding, drilling, and wiring standards, and eliminate hidden dangers through multi-stage inspections. At the same time, attention should be paid to industry standards (such as GB 7251.1 "Low Voltage Switchgear") to ensure that products meet certification requirements (such as CCC, CE), ultimately achieving the goal of "stable structure, reliable electrical, and safe operation".
