PLC control cabinet structure and principle

An industrial PLC cabinet refers to a complete electrical control cabinet that can realize automatic control of motors and switches. The equipment has overload, short circuit, phase loss protection and other functions, and has the characteristics of compact structure, stable operation and complete functions. According to the actual control scale, Programmable logic controller cabinets can be combined to realize automatic control of a single cabinet or to form a distributed control system through industrial Ethernet or fieldbus network. This product is widely used in electric power, metallurgy, chemical industry, papermaking, environmental protection, sewage treatment and other industries.

 

Automation control cabinet can complete equipment automation and process automation control, realize complete network functions, have stable performance, scalability, and strong anti-interference ability. Typical applications include constant pressure water supply, air compressors, fans and pumps, central air conditioners, port machinery, machine tools, boilers, paper machinery, food machinery, etc.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

The main components of an electrical control cabinet are as follows: Air switch: used to cut off and connect the power supply of the control cabinet. It is recommended to set up different circuit breakers for important electrical components. For example, set up a separate circuit breaker for the PLC and another circuit breaker for the contactor line. PLC: For simple logic control, a contactor can be used; for control with automatic control function or complex logic, PLC must be selected. If the project scale is small, an integrated PLC can be used, while if the project scale is large, a modular PLC is required.

 

24V DC switching power supply: refers to a DC regulated power supply whose power transistors work in a high-frequency switching state. The switching frequency is usually above 20kHz. If the Industrial PLC cabinet has a DC power input, a switching power supply must be configured. Most PLCs come with a 24V DC output, and you need to decide whether to install it based on the actual situation. Relay: For transistor output type PLC, if you want to drive AC load or power load, you need to use an external relay. The action process is that the PLC outputs to the relay coil, and the relay contacts drive the load. Terminal blocks: Used to achieve electrical connections. With the improvement of industrial automation, the usage of terminal blocks is gradually increasing. If other equipment is needed in the control cabinet, the number of circuit breakers can be increased according to the situation.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

The interior of the Enclosed PLC cabinet mainly contains the following units: 1. Power supply. The power supply system of PLC is crucial. When the AC voltage fluctuation is within the range of +10% (+15%), the PLC can be directly connected to the AC power grid without additional measures. The power supply mode is divided into AC 220V to DC 24V, and direct DC 24V power supply. 2. Central Processing Unit (CPU). The CPU is the control center of the PLC and works according to the functions assigned by the system program. It receives and stores user programs and data, checks the status of power, memory, I/O and watchdog timers, and diagnoses syntax errors in user programs. When put into operation, the PLC scans the input, reads the user program, executes and outputs the results.

 

3. Memory (PLC built-in). The memory that stores system software is called system program memory, and the memory that stores application software is called user program memory. 4. Input and output interface circuit. The input interface circuit inputs signals such as buttons, travel switches or sensors into the CPU and is divided into DC input circuit and AC input circuit. The DC input circuit has short delay time and is suitable for electronic devices such as proximity switches and photoelectric switches; the AC input circuit is suitable for harsh environments with oil mist and dust. The output interface circuit converts the signal output by the CPU into a signal that can drive external actuators. It usually uses optical coupling isolation technology and is divided into three types: relay output, transistor output and thyristor output.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

The physical properties of the cabinet directly affect the survivability of the PLC in harsh environments. In food processing or coastal high-humidity environments, it is recommended to use Stainless steel PLC cabinets (stainless steel PLC cabinets), whose excellent corrosion resistance far exceeds ordinary carbon steel spray cabinets. In general industrial plants, using a powder-coated PLC cabinet can provide sufficient anti-rust and insulation protection, and have a good appearance and texture. In addition, depending on the installation space limitations, you can choose a Wall-mounted PLC cabinet to save floor area or a Floor-standing PLC cabinet to accommodate more modules. For systems that require later expansion, Modular PLC cabinets provide excellent flexibility, allowing functional units to be added without replacing the main cabinet.

 

 

The company specializes in R&D and production of Standard PLC Cabinet of various specifications, and its products cover various industrial automation scenarios. We can provide customized design solutions according to customers' actual needs to ensure stable operation of equipment under complex working conditions. Welcome to contact us for detailed product information and technical consultation.