Drives and Controls Magazine
Modular PLCs combine redundancy and safety
Published:  28 June, 2018

Mitsubishi has announced that its Melsec iQ-R modular PLCs are now available as redundant pairs of controllers for extra reliability. The PLCs also include functions for monitoring and managing safety.

The PLCs comply with the requirements of IEC 61508 SIL 2 standard, which is designed to ensure that critical systems will continue to operate if there is a failure or accidental damage to the primary CPU. The standard requires a full duplicate PLC rack with all modules, to which the primary set can switch over instantaneously in an emergency.

Another layer of protection has been added to the basic redundancy architecture of the iQ-R. The safety version includes a SIL2-process CPU module and a separate SIL2-function module as a set, sitting alongside the power supply module, base and network module. This ensures continuous operation by switching to the standby set-up if an error occurs in the control system.

Mitsubishi's redundant PLC system provides instant switchover to a backup in the event of failure or damage to the primary PLC.

Mitsubishi’s GX Works3 programming platform combines process and safety-control programming in one environment. This allows integrated process-and safety-control programs to be executed by a single CPU module, eliminating the time and costs associated with buying and installing a separate safety controller.