Intended Use Of The Sto Function; Safety Characteristics; Possible Misuse Of The Sto Function; Diagnostics Coverage Range (Dc) Of The Motor Controller - Festo CMMO-­ST DION Série Description Et Mode D'emploi

CMMO­ST-...-DION/DIOP
1.1.2

Intended use of the STO function

The motor controller supports the STO safety function (Safe Torque Off ) in accordance with
EN 61800-5-2. The STO function is intended to disable the torque of a motor that is connected to the
CMMO-ST and prevent an unexpected restart of the motor. The STO function should only be used for
applications in which the specified safety characteristics are suffice.
1.1.3

Safety characteristics

The STO function of the CMMO-ST fulfils the requirements for the following safety characteristics:
– PL e/Cat. 3 according to EN ISO 13849-1
– SIL 3 according to EN 61800-5-2
– SIL CL 3 according to EN 62061
The achievable safety level depends on the other components that are used to realise the safety func­
tion.
To protect against unintended start-up, the motor controller must be activated via the connector [X3]
based on the category required for the application according to EN ISO 13849-1, e.g. by means of an
external safety switching device.
1.1.4

Possible misuse of the STO function

Unintended use includes the following applications:
– Bypassing of the safety function
– Use in applications where switching off can result in hazardous movements or conditions.
The STO function does not provide protection against electric shock, only against dangerous move­
ments!
1.1.5

Diagnostics coverage range (DC) of the motor controller

Diagnostic coverage (è Chapter 4) is influenced by how the motor controller is connected to the con­
trol chain as well as by the measures implemented for diagnostic purposes.
In order to achieve the diagnostic coverage, the status of the acknowledgment contact must be evalu­
ated by the control system with each request of the STO function.
If the signal does not correspond to the expected value, this can indicate a potentially dangerous mal­
function, e.g. a cable break. In this case, appropriate measures must be implemented to maintain the
safety level.
Note
The motor controller cannot detect a cross circuit in the input circuit by itself.
• Determine if cross-circuit detection for the input circuit and the connection wiring is
required in your application.
• If required, use a safety switching device with cross-circuit detection.
Festo – GDPC-CMMO­ST-EA-S1-Z6 – 2017-05d – English 25