THE PRINCIPLE :
The Warm magnet Interlock Controller is a PLC based system. It protects the normal conducting magnets from overheating by switching off the corresponding power converter when a fault occurs (magnet overheating, missing water flow…).
In order to satisfy the dependability requirements of such interlock functions, the Siemens “F” Series PLC is used, offering a self-verification environment that ensures the system integrity throughout operation. The WIC system performs self-testing of its own hardware and software to detect failures and memory corruption, and transits into a safe state in the event of an abnormality. The fail-safe state is to switch the Power-converters off as well as to request a beam dump/inhibit to the beam interlock system (BIS).
It should be noted that no analogue values are transmitted or processed by the WIC. Only digital information is considered (either OK or NOT OK). Signals are implemented in fail safe logic, meaning that a logic OK is always represented by an active input/output.
THE HARDWARE COMPONENTS :
The system is composed of 4 main building blocks:
The Power-Supply redundancy is assured through the use of two Power-Supplies: 24Volts - 10Amp, each connected to a redundancy module providing status information on the presence of the 24V from each power supply.
The CPU crate contains the CPU, a communication processor (CP) for the Ethernet connexion to the SCADA supervision system, a dedicated input module to read its own power-supply redundancy status and a dedicated output module to send the beam dump/inhibit signals. The chosen Controller (fail safe S7-315F-CPU from Siemens) offers a greater level of protection than a standard PLC, with a downside of an increased cycle time (and hence response time) in the order of ~ 100 ms.
Simplified layout of the WIC system (the magnet interlock boxes are not shown)
The Input crate contains safety input modules which collect signals from thermo-switches and flow-meters and output units used for delivering signals for remote tests of the input signals.
The Output crate contains modules which collect Status input signals from the Power converters and deliver the Power Permit signals to the power converters.
Note: Contrary to the input modules, the output modules are not of the safety type but are standard families. For that reason (concerning the Power Permit signals sent to Power-converters) two outputs of two different modules are connected in series to assure the required level of safety.
The PLC crate is connected via a Profibus-Safe link to the Input and Output crates.
For more details, please click here.