How to customize the design of PLC control cabinet

Complete process of customized design of PLC control cabinet (practical version)

First, the early demand confirmation (decide how to do the cabinet)

Control object and process

Equipment type: assembly line, machine tool, fan and water pump, servo, frequency conversion, hydraulic, etc.

Action logic: manual/automatic, linkage, interlock, emergency stop and alarm.

IO points: digital DI/DO, analog AI/AO, number of communication ports.

Site environment

Indoor/outdoor, dust, humidity, corrosion, temperature

Protection grade: general IP54, outdoor IP55~IP65.

Whether it is explosion-proof, anticorrosion and dustproof.

Power supply and electrical parameters

Voltage: AC220V/AC380V/DC24V.

Total power, maximum current, and whether reactive power compensation is needed.

Grounding requirements, lightning protection and surge protection

Communication and expansion

PLC brands: Siemens, Mitsubishi, Omron, Xinjie, Huichuan, etc.

Communication protocols: Modbus, Profinet, CC-Link, EtherNet/IP, 485/232.

Whether to connect touch screen, host computer, MES and cloud platform?

Second, the cabinet structure design

Size selection

According to the number of PLC, power supply, relay, terminal, driver and idle switch.

Common: 400×300, 500×400, 600×500, 800×600 and 1200×800.

20%~30% space is reserved for heat dissipation and later expansion.

Material and technology

Indoor: cold-rolled steel plate, plastic spraying.

Humidity/Chemical: Stainless Steel 304

The cabinet door is strengthened and the mounting plate is thickened to ensure rigidity.

Layout principle

Strong current is on the top/left and weak current is on the bottom/right.

PLC and module are centered, which is convenient for wiring.

Independent areas of power supply, filter and switching power supply

Separate wiring between strong and weak current to reduce interference.

III. Configuration of Electrical Components (Core Part)

main circuit

Total open → shunt open → contactor/thermal relay → motor/load

Separate loop of frequency converter and servo driver

control loop

PLC host+expansion module

DC24V switching power supply (power supply for PLC, sensor and solenoid valve)

Intermediate relay, terminal, safety, lightning protection/surge

Emergency stop, selector switch, indicator light and buzzer

safety design

Emergency stop normally closed circuit, independent hard wiring, without procedures.

Reliable grounding: cabinet grounding, system grounding and shielding grounding.

Overload, open phase, short circuit and leakage protection

Four, wiring and EMC anti-interference design

Wiring specification

The power line (380/220V) is separated from the signal line with a distance of ≥ 100 mm.

Shielded wire for analog signal, and single end of shielding layer is grounded.

The wiring shall be horizontal and vertical, with clear line number and neat binding.

interference protection measure

Incoming line plus filter and isolation transformer

Inverter output reactor

The metal cabinets are reliably communicated to form a shield.

The communication line shall be far away from the power line, so as to avoid parallel long-distance wiring.

V. Heat dissipation design

Low power cabinet: natural heat dissipation+ventilation louver

With frequency converter/servo: exhaust fan at the top and air inlet filter at the bottom.

High temperature environment or confined space: add cabinet air conditioner.

Six, logo and drawings

Component label, line number tube and loop name

Inside the cupboard door: electrical schematic diagram, wiring diagram and IO table.

Nameplate: model, power, current, protection grade and manufacturer.

Seven, the factory test

Insulation resistance test

Withstand voltage test

No-load electrification test

PLC program download and simulation debugging

Verification of interlocking, emergency stop and alarm functions