Application of the hottest Sifang e380 frequency c

Application of Sifang e380 frequency converter in cold rolling sheet line

Preface:

with the rapid development of computer information technology, the requirements of production process for production efficiency and production process are further improved. As a driver, frequency converter has been more and more widely used in the field of industrial automation. In the metallurgical cold rolling industry, the level of system integration and digital control determines the product quality and production efficiency, and also determines whether the manufacturer can occupy a place in the industry competition. The system composed of Sifang e380 series inverter, Mitsubishi FX2NPLC and Siemens DC drive, s is used in the cold rolling sheet line of an iron and steel plant in Foshan, which has reached the domestic advanced level in terms of system design reliability and process requirements. This paper will briefly introduce it and focus on the communication between Sifang inverter and Mitsubishi PLC in the system

scheme and control principle:

the drive parts of the production line, such as uncoiler, coiler, rolling host, etc., adopt DC separately excited motor, which is controlled by Siemens DC driver and Siemens PLC. Two 22KW AC motors are used for cooling and four 75kW AC motors are used for pickling. The AC motors are controlled by Sifang e380 series frequency converter and Mitsubishi PLC. Two sets of PLC systems are used as the lower computer, and the upper computer uses the configuration of king view to control the lower computer and monitor the site

the coolant of the whole production line is supplied by the above two cooling pumps and controlled and driven by a frequency converter. According to the requirements of production line speed and material thickness, the upper computer determines the required pressure and flow to be transmitted to PLC, and then PLC drives and controls the frequency converter. To ensure the process requirements, a pressure transmitter is used to feed back to the frequency converter for closed-loop control. PLC regularly sends PID set value to the frequency converter, and reads PID feedback parameters, motor output current and current output frequency for centralized processing. When the frequency converter operates to the upper limit frequency and the system pressure feedback signal fails to meet the requirements of the system, PLC switches the motor by reading the frequency converter parameters, and changes the motor from frequency conversion drive to power frequency drive by controlling the contactor. At the same time, the frequency converter starts the frequency conversion operation of the second motor, and the second motor is under PID closed-loop constant voltage control. On the contrary, when the feedback value is greater than the set value, the speed of the variable frequency motor decreases until the output lower limit frequency. If the feedback pressure is still greater than the set pressure, PLC will stop the drive of the second motor and switch the power frequency of the first motor to variable frequency PID closed-loop constant voltage control

four 75kW motors are divided into two groups and controlled by two frequency converters respectively. After the raw materials are heated in the production line, there is a layer of oxide on the surface. To remove this layer of oxide, it is necessary to use a certain proportion and pressure of acidic liquid to clean it before entering the next process. The two groups of acid pump motors clean the steel sheet at different positions according to different linear speeds. Similarly, the pressure transmitter is used to send the Ma signal to the frequency converter for feedback control. The control principle is the same as the previous two cooling pumps. The process of the whole production line is very rigorous. In order to improve the yield and production efficiency as much as possible, an electric contact pressure gauge is also installed in the main pipe of the three groups of pumps to set the upper limit pressure. When the pressure reaches the upper limit, the pressure gauge sends a signal, which is read by PLC and fed back to the upper computer to prompt the operator to deal with it in time

hardware communication

since Sifang inverter uses self-defined protocol communication and RS485 semi dual work as the physical electrical connection port, an additional fx2n-485bd board is required to communicate with Mitsubishi FX2N. The fx2n-485bd board uses the full duplex communication mode, so special treatment must be made on the wiring mode and internal program to properly communicate with the half duplex frequency converter. The last one shall be connected with a terminal resistance of 330 Ω. The wiring is as shown in the following figure:

program:

communication control commands of Sifang inverter are divided into six categories, and the frame header and frame footer of each group are hexadecimal data 5A and 0d respectively. In this example, the command to read the operation parameters is command 1, the length of the data transmission frame is 14 bytes, the command to modify the ram parameters is command 3, and the length of the transmission frame is 18 bytes. The control command is No. 4 command, the sending frame length is 15 bytes, and the inverter data return frame length is 18 bytes. The command used by Mitsubishi PLC for free port communication is RS command, and the special data register d8120 sets the corresponding parameters of PLC according to the communication parameters such as the communication format (such as parity check, baud rate) of the frequency converter. Considering that the host is in full duplex communication and the slave is in half duplex communication, the host will store the contents of the bytes sent in front of the receiving address while sending data, so special treatment shall be made on the internal receiving and sending address. The addresses d482-d499 receive the 18 bytes sent, and the data returned by the actual frequency converter from D500. If the maximum number of bytes to be sent is 15, the number of addresses to be received will be correspondingly increased by 3 to verify the torque whose lower measuring limit is 20% lower than the upper limit of the measuring spring change testing machine, and the number of bytes to be received will be correspondingly reduced by 3 to k33. Some procedures are as follows:

in this example, it is required to send and read multiple groups of data regularly in the stainless steel super large liner, while the RS command can only process the same event at the same time. Therefore, when sending and receiving a group of data, there must be a certain time interval before starting the next group of data processing. This requires the host to strictly distinguish the reading and sending of each group of data in time-sharing within the program. The program is as follows:

if it is necessary to read and write dozens of groups of data in some projects, it can be realized by calling subroutines when distinguishing the receiving and sending of automatic layering, forming, cutting and soaking groups of data. However, it is necessary to pay attention to the status of some bits when programming in this way. In this example, only one communication command is used. When receiving, it is necessary to distinguish which group of data is sent and the data returned by the frequency converter. Therefore, in the program, the index function should be used to verify and calculate the returned data. The program is as follows:

after the program is completed, the communication parameters of the frequency converter should be set, The main communication parameters of the frequency converter are set as follows:

f0.4:0002 (operation command channel) f8.0:0021 (PID control)

f8.1:0201 (PID setting and feedback channel selection) f9.0:0015 (communication setting)

f9.1: (set the address according to each station) f9.3:0000 (communication auxiliary function setting)

debugging:

the TA and TB ends of the frequency converter are set to alarm output, Send the alarm signal to PLC for monitoring on the upper computer. When a fault occurs, the operator can handle it quickly. During on-site debugging, the program shall be debugged in sections to improve the debugging speed. In case of problems, it is easy to solve. Special attention shall be paid to the fact that the received data can not be verified due to interference. Shielded double glue lines must be used on the communication lines, and the shielding layer shall be grounded

conclusion:

the upper computer is used for control and monitoring, and the lower computer PLC is used for communication control of the frequency converter. Through the exchange of dynamic data, the upper computer remotely monitors the frequency converter at any time. All data are clear on the screen. After debugging, the centralized operation of the effect display is very simple, the system operation is stable and reliable, and the integration degree is improved. The product quality and production efficiency are a difficulty in front of the scientific researchers and greatly improved