What should be paid attention to when processing the electrical control cabinet of sheet metal cabinet?

The machining of electrical control cabinet of sheet metal cabinet involves many dimensions, such as electrical safety, structural stability, equipment compatibility, etc., and it is necessary to take into account the machining accuracy and electrical function requirements. The following are the key points to pay attention to during processing:

I. Electrical Safety Compliance

The electrical control cabinet is directly related to the safety of electricity consumption, and it must strictly follow the industry standards (such as GB 5226.1-2019 Mechanical and Electrical Safety Mechanical and Electrical Equipment). The core precautions include:

Insulation and conductive isolation:

Metal components inside the cabinet (such as installation beams and guide rails) should be reliably connected with the grounding terminal, and the grounding resistance should be ≤4Ω to avoid the risk of electric leakage.

The distance between live parts (such as bus bars and terminal blocks) and the cabinet shell shall conform to the safety specifications: when the rated AC voltage is ≤380V, the air gap shall be ≥10mm, and the creepage distance shall be ≥12mm (it shall be increased by 20% in wet environment).

Protection against electric shock:

Openable parts such as cabinet doors and side plates need to be installed with braided grounding wires (cross-sectional area ≥ 4 mm) to ensure continuity of grounding when opening.

Burrs and sharp edges should be removed from the exposed metal surface to avoid scratching the cable insulation layer during installation or maintenance.

Fire and flame retardant:

The plates, coatings and cables used internally must be flame retardant: the coating of steel plate must pass UL94 V-0 flame retardant test, and the internal trunking is preferably made of flame retardant ABS material (oxygen index ≥28).

Second, the structural design and bearing rationality

The electrical control cabinet should bear the circuit breaker, PLC, frequency converter and other equipment, and the structural design should meet the mechanical and installation requirements:

Load distribution:

The bottom load-bearing components (such as beams and legs) should be cold-rolled steel plates with a thickness of ≥3mm, and the welded parts with the cabinet should be welded with reinforcing ribs (the thickness is the same as the main body, and the width is ≥50mm) to avoid the deformation of the cabinet caused by the heavy equipment.

The thickness of the internal mounting plate (used to fix the equipment) should be selected according to the weight of the equipment: 2.5mm steel plate for light equipment (≤50kg) and 4-6mm steel plate for heavy equipment (50-200kg), and it should be rigidly connected with the cabinet by bolts (≥4 fixing points per square meter).

Earthquake resistance and stability:

The verticality deviation of the cabinet is ≤1mm/m, and the overall diagonal deviation is ≤3mm (for the cabinet with a height of 2m), so as to prevent the equipment from tilting after installation.

The control cabinet in outdoor or vibration environment (such as workshop) needs to be equipped with shockproof foot pads (rubber material with hardness of 60±5 Shore A) or fixed by bottom bolts (the diameter of the connecting hole with the ground is ≥12mm).

Third, wiring and heat dissipation design

The cables in the control cabinet are dense, and the heating of the equipment is concentrated, so it is necessary to give consideration to the convenience of wiring and heat dissipation efficiency:

Wiring space planning:

Sufficient wiring channels shall be reserved: at least two independent wiring channels shall be designed in the vertical direction (strong current and weak current shall be separated, and the spacing shall be ≥30mm), and the slot width shall be determined according to the number of cables (the slot width shall be ≥50mm for every 10 10mm² cables).

The bending radius of cables shall be reserved at the joint between the cabinet door and the cabinet body: the bending radius of multi-strand cables shall be more than or equal to 10 times the cable diameter to avoid cable breakage caused by long-term opening and closing.

Heat dissipation and ventilation design:

According to the total power of the internal equipment, the heat dissipation demand is calculated: the ventilation volume should be ≥ 15m/h per 1kW power, the ventilation openings should be distributed up and down (bottom air inlet and top air outlet), and the air inlet should be equipped with a dustproof net (aperture ≤1mm) to prevent dust accumulation.

In high temperature environment (such as workshop control cabinet), the installation position of cooling fan or air conditioner should be reserved: the installation position of fan should be provided with deflector to avoid short circuit of air flow; The outdoor unit of air conditioner should be connected with the cabinet in a sealed way to prevent rainwater from infiltrating.

Four, machining accuracy and process adaptability

The precision of sheet metal processing directly affects the installation of equipment and the tightness of cabinet doors, and it needs to be controlled emphatically:

Dimensional tolerance control:

The length tolerance of the cabinet frame (column, beam) is ±0.5mm, and the verticality tolerance is ≤0.3mm/m, so as to ensure smooth splicing of all components.

Installation holes (such as equipment fixing holes and grounding screw holes) need to be processed by numerical control punching machine. The tolerance of hole position is ±0.2mm and the tolerance of hole spacing is ±0.3mm to avoid equipment installation dislocation.

Welding and bending process:

There should be no virtual welding and air holes at the welding place, and it should be polished flat after welding (roughness Ra≤12.5μm) to prevent the tip from discharging or scratching the cable.

Bending angle deviation ≤ 1, bending radius ≥ material thickness (for example, the bending radius of 2mm steel plate ≥2mm), so as to avoid cracking caused by stress concentration at the corner.

Surface treatment:

Exposed metal parts inside need phosphating treatment (film thickness is 5-10μm) to enhance conductivity and grounding reliability; The exterior should be sprayed with plastic (the coating thickness is 60-80μm), and the coating should cover the corners evenly, and the salt spray resistance test should be ≥ 48h (neutral salt spray standard).

V. Equipment Compatibility and Maintenance Convenience

The control cabinet should reserve space for installation, debugging and overhaul of internal equipment to avoid difficulties in later operation:

Space reservation:

The opening angle of the cupboard door is ≥ 120, and the distance between the cupboard door and the surrounding objects after opening is ≥500mm, which is convenient for internal equipment maintenance.

The distance between the equipment and the side wall and top of the cabinet should be ≥100mm (heat dissipation space), and the distance between the equipment and the cabinet door should be ≥80mm (to avoid the cabinet door squeezing cables).

Modular design:

Internally installed beams and guide rails shall be detachable (such as M6 bolts) to facilitate the position adjustment according to the equipment size.

Reserve spare holes (such as inlet and outlet holes and through-wall plates), the diameter of which should be 20% larger than the actual cable diameter, and be equipped with sealable rubber grommet to prevent cable wear.

Sixth, environmental adaptability

The design needs to be optimized according to the use scenarios (such as indoor, outdoor, dust/wet environment):

Outdoor protection:

The protection level of the cabinet should reach IP54 or above (dustproof+splash-proof). The sealing strip of the cabinet door is made of EPDM, with a cross-sectional diameter of ≥8mm and a compression of 30-40% to ensure reliable sealing.

The top should be designed with an inclined slope (≥ 5) and equipped with a rain eaves (≥100mm beyond the edge of the cabinet) to prevent rainwater from infiltrating.

Dust/corrosive environment:

Fully sealed structure is adopted, and the air inlet is equipped with a high-efficiency filter (filtration accuracy ≥5μm) and a positive pressure ventilation system (internal air pressure is 5-10Pa higher than external air pressure) to prevent dust from entering.

In highly corrosive environment (such as chemical workshop), 304 stainless steel cabinet (thickness ≥2mm) should be selected, and the welding place should be passivated by pickling to avoid corrosion.

summary

The processing of the electrical control cabinet of sheet metal cabinet should take * * "safety first, functional adaptation and reliable technology" * * as the core: it should not only meet the electrical safety standards (grounding, insulation and flame retardant), but also ensure the structural load-bearing and heat dissipation efficiency, and at the same time ensure the equipment compatibility and maintenance convenience through high-precision processing. Different scenes (such as industrial workshops and outdoor base stations) need to optimize the protection design, and finally achieve the goal of "safety, stability and durability".