Abstract : This paper focuses on the construction, design, and application of a PLC as the control unit in a paper machine drive system. It achieves fully digital fieldbus control of the drive system, with a frequency converter as the execution unit, by the PLC, fulfilling the requirements for speed chain synchronization, load distribution, and tension control at each drive point of the paper machine. Keywords : PLC; frequency converter; fieldbus In the field of control applications for paper machine drives, with the widespread application of frequency conversion technology, computer technology, and network communication technology, the automation level, control accuracy, control speed, system stability, and reliability of paper mills have been improved to a new level. This paper focuses on the design and application of the Siemens 200 PLC in a paper machine drive system. 1 System Construction The programmable logic controller (PLC) and the frequency converter constitute a DCS system, as shown in Figure 1. The system uses relays to control the start, stop, emergency stop, and crawl/run of each transmission point, while the paper machine speed increase/decrease and tension/loosening are controlled by a PLC. It also fulfills the requirements for multi-drive speed chain control and load distribution control of the load-sharing transmission points. The PLC acquires the above signals, performs calculations to obtain the motor's running speed setpoint, and then writes it to the frequency converter as a frequency signal output via the RS-485 bus. Simultaneously, the PLC adjusts its processing program according to the open/closed-loop signals to adapt to the open/closed-loop control requirements. [b][align=center]For more details, please click: Application of PLC in Paper Machine Drive Control[/align][/b]