Abstract: This paper focuses on the change of the converter feeding system from Momentum control mode to Quantum PLC remote station control mode, and explains the advantages of PLC remote station control mode.
Keywords: Control, PLC, Communication
The PLC Control System Optimizing of 120T Convertor Feeding
(NO.3 Steel-making plant of Jigang Ltd. Co., Jinan 250101, China )
Abstract: The text introduces Converter feeding system, its control mode is changed from Momentum to the RIO of PLC, and the RIO strongpoint is shown.
Key word: control, PLC, Communication
1. Overview
The PLC for the charging system of the No. 1 120t converter in the No. 3 steelmaking plant of Jinan Iron and Steel Group adopts Schneider Electric's Modicon TSX Quantum PLC, a high-end industrial automation control system, as its control core. This series of products is not only of high quality and reliable performance, but also highly compatible. The charging scheme for the No. 1 converter uses Schneider Momentum modules and employs Peer Cop communication. All control panels and field control boxes communicate with the PLC using Momentum I/O modules. Weighing signals for bulk materials and alloy materials are directly fed into the PLC via Momentum weighing modules, while speed control signals for the frequency converter are sent to the frequency converter through Momentum analog output modules.
With the successful commissioning and full production of the No. 1 120t converter, the mode of using Schneider Momentum series Peer Cop communication and exchanging data with the main PLC for feeding via MB+ network has exposed many problems:
● Poor shock resistance; TAP junction boxes are prone to poor contact, causing communication failures.
● The product has high requirements for the application environment, poor durability, and a high failure rate.
● The product has limited functionality and cannot clearly indicate faults.
● The MB+ network wiring is complex, making troubleshooting difficult and hindering the rapid resolution of on-site problems.
Since the No. 1 120t converter was put into operation, similar problems have occurred multiple times in the feeding system, directly causing network communication failures. Furthermore, the fault indications are unclear, and troubleshooting is time-consuming and difficult, severely restricting the production pace.
2. Introduction to the feeding system
The initial design of the PLC for the No. 1 120t converter feeding system adopted Schneider Electric's Quantum series automatic control products. The Quantum series features a modular and scalable architecture. Considering the large number of devices and complex operation of the feeding system, the design required all signals from the control panel, field control boxes, and material weighing to communicate with the main PLC CPU via MB+ network using Momentum modules and token-based transmission. The Momentum series modules are a relatively inexpensive PLC product from Schneider Electric, generally composed of I/O boards, communication adapters, and terminal blocks. The original feeding system consisted of 23 Momentum subsystems, communicating with the main PLC CPU via MB+ network and using Peer Cop point-to-point communication for data transmission. The biggest problem with this transmission method is its high dependence on the master station, increasing the burden on the main PLC CPU and potentially leading to data loss under certain circumstances, as well as poor network stability. The 23 Momentum I/O modules are configured in seven different power distribution cabinets, and the six Momentum weighing modules are configured in electrical cabinets on different platforms in the field. The configuration structure is shown in Figure 1.
Figure 1: PLC structure configuration diagram using MB+ communication method
The system includes 11 170ADI35000 digital input modules, 6 170ADO35000 digital output modules, 6 170AAO92100 analog output modules, and 6 170ISP00100 weighing modules.
However, during the normal operation of our equipment, we discovered a very significant hidden danger. The MB+ network in the feeding system uses shielded twisted-pair cables. A short circuit or open circuit in these cables will paralyze the entire network. Therefore, protecting the normal operation of the MB+ network is crucial. Referring to Figure 1, each Momentum module in the network segment corresponds to an MB+ splitter 990NAD23000, also called a TAP connector. The TAP connector serves as a connecting element. Its structure is shown in Figure 2:
Figure 2: TAP head structure diagram
Each TAP head contains 13 twist-lock terminals. Accurate and reliable connection of each terminal is crucial; otherwise, the entire MB+ network will fail. The twist-lock wiring is a key factor restricting the stable operation of the feeding system. Each communication cable is approximately 1 mm in diameter and is crimped to the terminal using a plastic cap. There is no means to detect the wiring status (on/off); checking the wiring requires removing the plastic cap and re-crimping. Remaking a new TAP head takes approximately 20 minutes. Furthermore, the MB+ network lacks clear fault indicators; troubleshooting requires checking every connection within the TAP head, resulting in a large workload, long processing time, and reduced production efficiency.
Due to the instability of the main PLC CPU and the inherent unreliability of the TAP head, and while maintaining the steelmaking feeding process requirements, and based on on-site control site observations and adhering to the principles of reliability, advancement, and safety, it was decided to optimize the No. 1 converter feeding control system. The system will be upgraded from Momentum control mode to Quantum series remote station control mode, achieving dual-channel redundant communication. This upgrade will improve communication reliability and reduce the failure rate.
3. Implement using the Quantum automation platform
The Quantum automatic control system is easy to configure, wire, and maintain; it offers excellent isolation, a robust structure, corrosion resistance, and adaptability to harsh industrial environments. All components are hot-swappable and interchangeable. The control system not only features reliable hardware but also powerful, reliable, and user-friendly system software (MonitorPro V7) and programming software (CONCEPT).
The Momentum system for charging the No. 1 converter was transformed into a Quantum series remote station, mainly including the design of the automatic control system, as well as the writing, modification and debugging of the program.
3.1 Design of Automatic Control System (Hardware Modification)
For the design of the automatic control system, while keeping the equipment control procedures unchanged, the principle of minimizing modifications to the hardware and software systems is followed to achieve a comprehensive improvement in practicality and reliability, fully meeting the on-site requirements. The modified network structure is shown in Figure 3:
Figure 3 shows the PLC structure configuration using remote station communication.
Based on a comparative analysis of Figures 1 and 3, this solution transforms the production line's automatic control system from the original Momentum series network structure to a Quantum series remote station network structure. The PLC remote stations are connected via a Modbus network to achieve system data exchange and communication. A comparative analysis of the functional characteristics of the Momentum and Quantum modules leads to the replacement of the original Momentum modules with the following modules:
The modified modules are large and occupy a lot of space. Therefore, an additional PLC cabinet is needed, using CableFast terminal blocks for connection, with a double-row 16-slot rack to form two remote stations. The 170ISP00100 is responsible for real-time acquisition of weighing signals from the weighing hoppers and is installed in control boxes on different platforms on-site. Due to the wide distribution of weighing equipment and the long distance between it and the PLC control cabinet, the six weighing modules were not modified in this project.
3.2 Software and Program Modification
The host computer uses the Windows XP operating system, the PLC programming software is Concept 2.6, and the host monitoring software is MonitorPro V7. The original Peer Cop network configuration was deleted, and a new RIO configuration was added. The register addresses were reallocated in the program, and communication variables passing through the Peer Cop were converted into I/O read/write variables to achieve network conversion. The program modification is shown in Figure 4.
Figure 4
By converting the code, extensive modifications to the program are avoided, and the monitoring of communication status is enhanced. This provides excellent guidance for network fault diagnosis and significantly reduces network fault handling time.
3.3 System Construction Plan
Install the new PLC cabinet. Remove the Momentum series modules from the original distribution cabinet and replace them with terminal blocks, which are then connected to the new PLC cabinet via multi-core cables. Remove the existing MB+ network cables and lay new coaxial cables. The new PLC cabinet remote station is connected to the master station CPU via a coaxial cable to enable data communication between the master and slave stations.
4. Conclusion
The PLC of the No. 1 converter charging system at Jinan Iron and Steel Group's Third Steelmaking Plant was successfully put into use after this optimization and upgrade. Its operation has been excellent, maintaining a zero-failure rate, laying a solid foundation for the stable and high-yield production of the Third Steelmaking Plant. This also fully demonstrates the stability, reliability, and practicality of the Quantum automatic control system.
About the author:
Zhang Liang (July 1979 - ), female, engineer, mainly engaged in the research and application of converter electrical automation technology.
Contact information:
Address: Electrical Automation Workshop, No. 3 Steelmaking Plant, Jinan Iron and Steel Group, Jinan City, Shandong Province, 250101, China
Email: [email protected]
Telephone: 0531-88847025/88847105
Mobile phone: 13864105869
