SIL 2 Power Contactors

Last edit: 03/07/2023

Some manufacturers have power contactors in their range  that contain a  bit of electronics. That allows the component to be defined as type B. Moreover, an SFF > 90 % is attributer to the contactor, both in High and in Low demand mode of operation.

That means they can be used without redundancy (HFT = 0) and the output subsystem can reach SIL 2.

We recommend that, in case of HFT = 0, the maximum SIL be limited to 1.

The reason is also because, the same component is declared PL c according ISO 13849-1.

That difference (SIl 2 according to IE 62061 and PL c), was made possible with the first edition of IEC 62061; with the second edition that “approach” is not recommended.