PM803F ABB

(3) Communication functions

 

Large and medium-sized PLC systems should support a variety of fieldbuses and standard communication protocols (such as TCP/IP), and should be able to connect with the factory management network (TCP/IP) when needed. The communication protocol shall comply with ISO/IEEE communication standards and shall be an open communication network.

 

The communication interface of PLC system should include serial and parallel communication interface (RS2232C/422A/423/485), RIO communication interface, industrial Ethernet, common DCS interface, etc. Large and medium-sized PLC communication bus (including interface equipment and cables) should be 1:1 redundant configuration, the communication bus should meet the standards, and the communication distance should meet the actual requirements of the device.

 

In the communication network of the PLC system, the superior network communication rate should be greater than 1Mbps, and the communication load should not be greater than 60%. The communication network of PLC system has the following forms: 1) PC as the main station, many PLC of the same type as the slave station, to form a simple PLC network; 2) One PLC is the main station, and other PLC of the same model is the slave station, which constitutes the master-slave PLC network; 3) The PLC network is connected to a large DCS as a DCS subnet through a specific network interface; 4) Dedicated PLC network (dedicated PLC communication network of various manufacturers).

 

In order to reduce the communication task, according to the actual needs of the network composition, communication processors with different communication functions (such as point-to-point, fieldbus, industrial Ethernet) should be selected.

 

(4) Programming function

 

Offline programming mode: PLC and programmer share a common, programmer in programming mode, only to provide services for the programmer, not to control the field equipment. After the programming is completed, the programmer switches to the running mode to control the field equipment and cannot be programmed. The off-line programming method can reduce the system cost, but it is not convenient to use and debug. Online programming mode: and the programmer have their own, the host is responsible for field control, and in a scanning cycle with the programmer for data exchange, the programmer to the online preparation of the program or data sent to the host, the next scanning cycle, the host according to the newly received program run. This method has high cost, but the system debugging and operation are convenient, and it is often used in large and medium-sized PLCS.

 

Five standardized programming languages: Sequence Function diagram (SFC), ladder diagram (LD), function module diagram (FBD) three graphical languages and statement table (IL), structure text (ST) two text languages. The selected programming language should comply with its standards (IEC6113123), and at the same time, it should also support a variety of language programming forms, such as C, Basic, etc., to meet the control requirements of special control occasions.

 

(5) Diagnostic function

 

The diagnostic function of PLC includes hardware and software diagnosis. Hardware diagnosis The hardware fault location is determined by the logical judgment of the hardware. Software diagnosis includes internal diagnosis and external diagnosis. The diagnosis of PLC’s internal energy and function through software is internal diagnosis, and the diagnosis of PLC’s exchange function with external input and output components through software is external diagnosis.

 

The strength of the PLC diagnostic function directly affects the requirements for operation and maintenance technical capabilities, and affects the average maintenance time.

 

(6) Processing speed

 

PLC adopts scanning mode to work. From the perspective of real-time requirements, the processing speed should be as fast as possible, if the signal duration is less than the scanning time, the PLC will not scan the signal, resulting in the loss of signal data.

Fanuc A06B-0147-B177 AC Servo Motor A22/2000 3.8 kW 3PH

Square D I-Line NC361200 NC-361200 NA 1200 Amp 1200A A

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C-H CH Westinghouse HND3800T107W Optim 800 Amp 800A A

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Toshiba Houston TEFC Motor 200 HP 1770 RPM Fr. 447TZ

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