The so-called PLC control is programmable control. Most of the controls are programmed. Therefore, the wiring is more concise, and the control logic can be modified by programming at any time.In addition to the control function of the relay, the analog signals such as voltage, current, pressure and temperature can be collected and quantized into the control loop through various interfaces. It can output various signals such as switching value, analog value and pulse. It can cooperate with step and server to achieve accurate motion control. Human machine interface (HMI) control can be realized: human machine interaction control can be realized with touch screen and industrial control computer. It has a variety of communication interfaces, which can realize interconnection and mutual control among multiple control sites. Remote monitoring can be realized through network port.
PLC control cabinet has overload, short circuit, phase loss protection and other protection functions. It has compact structure, stable operation and complete functions. It can be combined according to the actual control scale, which can not only realize the automatic control of single cabinet, but also realize the DCS control system composed of multiple cabinets through industrial Ethernet or industrial field bus network. PLC control cabinet can adapt to various industrial automation control occasions. It is used in electric power, metallurgy, chemical industry, paper making, environmental protection sewage treatment and other industries.
PLC control cabinet generally includes the following five parts:
1. Air switch. A general air switch, this is the power control of the whole cabinet.
2. PLC. This should be selected according to the needs of the project. For example, if the project is small, it can be an integrated PLC directly, but if the project is large, it may need modules, cards, and redundancy (that is, two sets of alternating use).
3. Power supply. For a 24VDC switching power supply, most PLCs are equipped with their own 24VDC power supply. Whether to use this switching power supply depends on whether it is really necessary.
4. Relay. In general, PLC can send instructions directly to the control circuit, but it may be transferred by relay first.
5. Terminal block. It refers to secondary line terminal and primary element terminal.
Service conditions of PCL control cabinet
Power supply: DC 24V, single-phase AC 220V (- 10%, + 15%), 50Hz. Protection grade: IP41 or IP20
Environmental conditions: the ambient temperature is 0 ℃ - 55 ℃, to prevent direct sunlight; the relative humidity of air shall be less than 85% (no condensation). Keep away from strong vibration source and prevent frequent or continuous vibration with vibration frequency of 10-55hz. Avoid corrosive and flammable gases.