Introduction  Neutral beam injection (NBI) is an important means of plasma heating and current driving on HL-3 Tokamak. The NBI heating system involves multiple disciplines and fields such as vacuum, power electronics, mechanics, automatic control, and gas discharge. The control system is the basic guarantee for the reliable operation of the NBI heating system, enabling remote control of the field equipment of the heating system, the real-time monitoring of the running state, and the logic control of the discharge experiment.

  Method  The hardware configuration of the PLC system was determined based on the requirement of NBI heating beamline, and the distributed I/O system was set up with Siemens S7-416 as the main controller, Profibus-DP network and industrial Ethernet as the basis, and optical fiber as the transmission medium. Configuration software STEP7 was used to realize hardware configuration, communication connection, and program writing, and interface software WinCC was used to complete centralized management, process monitoring, and information archiving.

  Result  The PLC system can monitor the field equipment status in real time, exchange data with the NBI control system, and instruct field devices to work stably. In addition, the graphical user interface can realize the visualization of experiment processes and real-time display of vacuum value, flow rate, and temperature, providing timely state information for operators.

  Conclusion  The whole PLC system is efficient, reliable, reproducible, well-compatible, and scalable, which can be used to monitor and control the field equipment of the NBI beamline.