Requirements for the operation of the STO safety sub-function

  • Operation is only permitted within the limits specified on the data sheets. This applies to the external safety controller as well as to the device and the approved safety options.
  • The built-in diagnostic function is limited in the case of a permanently enabled or permanently disabled STO input. Advanced diagnostic functions are performed only upon a level change of the STO signal. The safety sub-function must therefore be requested via the STO input for PL d in accordance with EN ISO 13849-1 and SIL 2 in accordance with EN 61800-5-2 at least once every 12 months, and for PL e in accordance with EN ISO 13849-1 and SIL 3 in accordance with EN 61800-5-2 at least once every 3 months with the line voltage applied in order to achieve full test coverage. Adhere to the following test procedure for this.

  • [1]

    Maximum 12 months with PL d/SIL 2

    Maximum 3 months with PL e/SIL 3

    [2]

    Internal diagnostics

    [3]

    High: No STO

    [4]

    Low: STO active

  • To achieve complete test coverage after a device reset (e.g. after switching on the supply voltage), the test transition (STO active → STO not active) may be started after > 700 ms at the earliest. The device signals the "ready for operation" or "STO – Safe Torque Off" state if it is not in fault state.
  • A detected hardware fault in the internal switch-off channels for STO will lead to a locking fault state in the device. If the fault is reset (e.g. by switching the supply voltage on/off or by a low level at the STO input for at least 30 ms), a complete test with internal diagnostics according to the above-mentioned test procedure must be performed. If the error occurs again, replace the device or contact SEW‑EURODRIVE Service.