PLC-based interlock system for superconducting magnets

The development of an electrical hazard interlock system based on dual redundant programmable logic controllers (PLCs) is described. Sensitive I/O is implemented and processed in a redundant fashion. The PLCs make sure that terminal covers cannot be opened while dangerous currents are flowing, and they redundantly shut off the power supplies if any interlock violations, faults in the I/O circuits, or problems in the PLC system itself are detected. A first version of the software running on a single CPU has been developed and is being adapted and finalized for installation in the final PLC systems. A description is given of the application, the PLC system, the software architecture, and the hardware and software redundancy schemes. >