How to design the internal layout of electrical control cabinet of sheet metal cabinet?

The internal layout design of the electrical control cabinet of sheet metal cabinet directly affects the stability of equipment operation, wiring efficiency, heat dissipation effect and convenience of later maintenance, and needs to be comprehensively planned in combination with electrical principles, equipment characteristics and operation requirements. The following are specific design points:

First, the core principles of layout design

Safety first

Strong current (power circuit, such as circuit breaker and contactor) and weak current (control circuit, such as PLC and sensor) shall be strictly partitioned, and the distance shall be ≥300mm to avoid electromagnetic interference (such as signal interference of frequency converter to PLC).

High-voltage components (such as the main circuit breaker of the incoming cabinet) shall be isolated independently, and protective baffles (steel plates with thickness ≥2mm) shall be set, and the distance from the accessible area of the operator shall be ≥500mm.

Clear functional partition

Divide the areas (such as incoming line area, power distribution area, control area and output area) according to the logic of electrical circuit, ensure that the path from incoming line to load is clear, and reduce cable crossover.

Heat dissipation and smooth airflow

Heating equipment (such as frequency converter and power supply module) is centrally arranged in the upper or rear part of the cabinet (hot air rises), and low-temperature equipment (such as relays and terminal strips) is arranged in the middle and lower part, forming an air flow channel of "lower inlet and upper outlet".

Second, the partition layout design details

1. Bottom area (load bearing and incoming line)

Function: Carrying heavy equipment, incoming cable access and grounding system.

Layout points:

When placing heavy equipment (such as main circuit breaker and reactor), it should be close to the bottom beam (bearing fulcrum) of the cabinet, and the contact area between the bottom of the equipment and the cabinet should be ≥ 80% of the bottom area of the equipment to avoid single point stress.

The wire inlet hole is opened at the center or side of the bottom of the cabinet, and the diameter of the hole is 20% larger than that of the cable, and waterproof glen head (outdoor cabinet) or wire protector (indoor cabinet) is installed to prevent the cable from being worn.

The grounding terminal block (cross-sectional area ≥ 10 mm) is fixed on the inner side of the bottom, directly connected with the grounding bolts (M8 and above) of the cabinet, and clearly marked (yellow-green).

2. Central Region (Core Control and Distribution)

Function: Installation of control unit, power distribution module, terminal strip, etc. It is the main area for operation and maintenance.

Layout points:

Control unit (PLC, HMI, relay):

It shall be arranged at a height of 1.2-1.6m (comfortable area for human operation), and the HMI (touch screen) shall be parallel to the cabinet door, with an inclination angle of ≤ 15 (convenient for viewing), and a space of ≥100mm shall be reserved around it for wiring and operation.

PLC modules are arranged horizontally, and the distance between adjacent modules is ≥20mm (heat dissipation). Input and output modules are grouped according to signal types (such as digital quantity and analog quantity).

Power distribution and terminal strip:

The AC terminal strip and the DC terminal strip are arranged separately, and the spacing is ≥ 50 mm; The high-voltage terminal (≥10A) is at the bottom and the low-voltage terminal (≤5A) is at the top, so as to avoid touching the high-voltage by mistake when plugging and unplugging.

The length of the terminal block is designed according to the number of cables, and every 50 terminals are reserved with a redundant space of ≥100mm, which is clearly marked (the wire number and loop number correspond to the electrical drawings).

3. Upper area (heat dissipation and high-frequency equipment)

Function: install heating equipment, heat dissipation device and high frequency module.

Layout points:

Heating equipment (frequency converter, servo driver, power module):

The horizontal spacing shall be ≥100mm, and the distance between the vertical and the top shall be ≥200mm (reserved heat dissipation space). If the power is ≥5kW, a deflector (guiding hot air to the top air outlet) shall be installed.

The air inlet of the inverter faces the lower part of the cabinet (take cold air), and the air outlet faces the back or top of the cabinet (remove heat) to avoid hot air circulation.

Heat sink (fan, air conditioner):

An axial fan is installed at the top (air volume ≥ 1.2 times of the total heat dissipation requirement of the equipment), and a dustproof net (detachable cleaning) is installed below the fan; The side-mounted air conditioner should be close to the heating equipment, and the air outlet is facing the heat source.

4. Rear and Side (Wiring Channel)

Wiring trough design:

Vertical direction: 3-4 independent trunking (high-voltage, low-voltage and communication lines are separated) are installed on both sides or at the rear of the cabinet, and the width of the trunking is ≥80mm (to accommodate cables below 10mm²), and fixed buckles are set in the trunking every 300mm (to prevent cables from shaking).

Horizontal direction: install transverse trunking (connecting vertical trunking) under the equipment, and adopt circular arc transition at the corner (avoid cable breakage, and the bending radius is ≥10 times the cable diameter).

Reserved threading hole:

The threading hole on the equipment installation plate should correspond to the trunking. The diameter of aperture ratio cable is 20% larger, and the rubber retainer (cut-proof insulating layer) is installed at the edge of the hole.

Third, the layout adjustment of special scenes

Compact control cabinet (limited space)

Layered mounting plates (upper and lower floors, spacing ≥300mm) are adopted, with light control equipment on the upper floor, heavy power distribution equipment on the lower floor, and partitions (with ventilation holes) in the middle to separate high current/weak current.

Cables shall be fixed with wire harness (spacing ≤200mm), so as to reduce the space occupied by trunking, but it is necessary to ensure that the diameter of single-bundle cable is ≤ 70% of the width of trunking (heat dissipation gap is reserved).

Outdoor/dustproof control cabinet

The internal equipment is centrally arranged in the middle of the cabinet to avoid being close to the cabinet door (to reduce dust entry when opening the door), and the wire inlet hole at the bottom needs to be sealed (double protection with sealing rubber ring and glen head).

Cancel the side open trunking and use closed metal trunking (with cover plate) to prevent dust accumulation.

Vibration environment (e.g. workshop, machine tool)

The equipment and the mounting plate are fixed by bolts+shockproof pads (rubber material, thickness 5-10mm), the terminal strip is selected with locknuts, and cold-pressed terminals+insulating sheaths are used at both ends of the cable (to prevent poor contact caused by vibration).

Fourth, optimization of maintenance convenience

Accessibility of equipment: Common operating equipment (such as emergency stop button and indicator light) is installed in the cabinet door or within 1.5m height, and the equipment that needs regular maintenance (such as air switch and fuse) is reserved with an operating space of ≥600mm (it can be fully operated by reaching out after opening the door).

Marking and recording: the layout drawing is pasted inside the cabinet (indicating the name, location and number of the equipment), the cable usage (such as "PLC input" and "motor power supply") is marked next to the trunking, and the terminal block corresponds to the drawing number (convenient for line checking).

summary

The internal layout of the electrical control cabinet needs to balance the four elements of "functional logic, heat dissipation efficiency, safe distance and wiring convenience": isolate strong current and weak current by zones, centrally arrange heating equipment and plan independent wiring channels to ensure the stable operation of the equipment; At the same time, the operating height, maintenance space and identification clarity are taken into account to reduce the later operation and maintenance costs. After the layout design is completed, it is suggested to simulate the equipment installation and cable direction through three-dimensional modeling (such as SolidWorks) to find the interference problem in advance.