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Application of man-machine interface in intelligent silicon controlled rectifier

1 system composition and working principle

1.1 system composition

the system is composed of five parts: transmitter, PLC host, analog input and output module, touch screen, silicon controlled rectifier, etc. the system control structure is shown in Figure 1. In the control part, Siemens's PLC is selected to process the sampling signal quickly and reliably, and the programming software is step 7-microwin 32 v3.2; Tp270b touch human machine interface (HMI) of Siemens is selected to display and record real-time temperature values and various fault information. The configuration software is SIMATIC Pro tool V6.0. MPI (multipoint) communication mode is adopted between HMI and PLC. Through the definition of component attributes set on HMI screen and data exchange address with PLC, the register corresponding to relevant components on HMI can read and write PLC storage unit

Figure 1 system control structure

1.2 working principle

silicon controlled rectifier output DC voltage, 0 ~ 45V continuously adjustable; Output DC current, 0 ~ 1600A continuously adjustable. The temperature of the main silicon element is sampled by the sensor, and the measured temperature signal is sent to PLC after amplification and a/D conversion. The data is processed by software, and the processed data is sent to HMI for real-time display. Set the temperature limit value of over temperature alarm and over temperature trip on HMI. When the main circuit silicon element temperature is too high and exceeds the limit value, PLC will output overtemperature alarm signal and overtemperature trip signal, and display specific information on HMI. At the same time, the current and voltage of the excitation coil are accurately PI controlled, and the parameter values of PI algorithm can be set on HMI. The data acquisition and processing, fan operation and fault alarm in the system are completed by PLC and HMI through the preparation of corresponding software

2 software design of the system

simatic protool is the HMI configuration software launched by Siemens. The software is composed of two well-known iPhone 5/5s parts: protoolcs (configuration system) and protool RT (operation system) for process visualization with too low oil viscosity (oil flow continuously from the oil delivery valve return pipe during loading). The software has many functions, such as alarm recording, report printing, trend curve and so on, and supports the communication protocol of third-party manufacturers except Siemens. Based on it, this system has developed a series of applications, such as image design, communication configuration, alarm setting, security protection design and so on

2.1 touch screen picture design

touch screen picture design not only requires to realize all control functions (input and display parameters, storage records, alarms, etc.), but also to be simple and clear, easy for operators to correctly perform operations. Considering the process variables and actual functions that the system needs to monitor, a total of five groups of pictures are configured, and several basic pictures are introduced below

⑴ main screen

the top of the designed monitoring main screen is the excitation current real-time display curve, and below it are two display boxes that display the excitation current and voltage values in real time. There is also an input box for setting the current value. When you press this position, the digital option box will pop up to facilitate the input of the current setting value. There are two fine adjustment keys on the right side of the box. Each time you press it, you can add 1 or subtract 1. At the bottom of the main control interface is the equipment operation status display box, which can display the status of the system in real time (system on, off, whether there is fault and other information). In the lower right corner of the monitoring main screen is the function selection pop-up menu, which is mainly composed of the working status bar, parameter setting bar, alarm record bar, etc. As shown in Figure 2

Figure 2: monitoring main screen

(2) real time display of temperature, current and voltage

when displaying, the touch screen reads only one digital value from the PLC at a time in each time unit (clock pulse) and adds it to the corresponding physical value displayed on the operation unit. In this program, three groups of real-time data are configured, and each group displays three analog quantities of temperature, excitation current and voltage of silicon main components

⑶ parameter setting

in this screen, the operator can set and adjust the automatic start/stop temperature of the fan, the overtemperature alarm temperature and overtemperature trip temperature of the silicon main element, as well as the overcurrent value and overvoltage value. The operator with the highest authority can also set the parameters () in the PID algorithm, which makes it convenient to set the parameters of the system

⑷ fault record

whenever an alarm signal is generated, an alarm message window will pop up on the touch screen interface, and the alarm light will flash at the same time. Archive the alarm messages, and then create a picture of the configuration messages as long as the heating time, you can save and display all the alarm messages since the operation of the system. Prompt the alarm number, the date and time of the alarm, the reason of the alarm, and whether to confirm it

2.2 security protection design

protool allows users to use passwords to prevent other unauthorized people from using controls, thereby increasing the security of the system. The password level provided by protool ranges from 0 to 9. These policies have an impact on the development of enterprises, and the command level 0 does not need to enter a password; The password level is 1 to 8, which is allocated according to the importance of the function; Password level 9 is only authorized by the system administrator. For the needs of security management and operation, the system defines two levels of passwords: system administrator level 9 and operator level 1. For PID parameter setting, the system administrator level password should be used. For other operations, such as temperature alarm limit, startup soft start time, etc., the password should also be entered first to log in. Enter the password, touch the "login" button, and then touch other function buttons to enter the sub screen equal to or lower than the password level. After returning to the main screen after the operation of the sub screen is completed, touch the "exit" button, and the password will be invalid. To enter the sub screen again, you need to re-enter the password. If the "exit" button is not touched, the system will automatically revoke the password after 1min

2.3 communication between human-machine interface and PLC

there are three communication modes between Siemens human-machine interface and PLC: PPI (point-to-point) communication mode, MPI (multipoint) communication mode and PROFIBUS-DP communication mode

MPI (multipoint) communication mode is adopted in this system. Because MPI interface is of RS485 structure, PLC and human-machine interface are connected through RS485 line, and its transmission rate is 187.5k baud rate. An MPI can have multiple network nodes, and its address is set in the s hardware configuration. The MPI address of man-machine interface in the system is "1"; The MPI address of CPU is "2". The man-machine interface communicates with the process through PLC using variables. Generally, the data exchanged between PLC and operation unit is process data. To do this, create a variable in the configuration that points to an address on the PLC. The touch screen reads the value from the specified address and displays it. Similarly, the operator can input the data to be written to an address on the PLC on the touch screen

3 conclusion

1600a/45V intelligent silicon controlled rectifier combines PLC and touch screen, and uses the corresponding software of PLC and touch screen to control and process each sampling value. It has great advantages in real-time display of temperature, current and voltage, data recording, alarm and so on. The operator can not only conveniently observe and master the real-time operating temperature of the device, but also quickly troubleshoot according to the alarm message; With the help of historical records, managers can also analyze and query important data, which can greatly improve the level of operation management. At present, the device has been applied in Ganzhou Jinhuan magnetic separation equipment Co., Ltd. (end)

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