07-02-12-02-EN-V1215.doc / Type: 638
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9.4 Application Example of STO (Safe Torque Off)
Minimal request of safety function by Cat. 3 and PL d
The safety function STO must activate for at least weekly.
This request is very important for application continuous operation and is satisfy by open the guard door and
activate the emergency stop. If the Safe torque off is activate very often, additional measures are not
necessary.
(Only if the Guard door and/or the emergency stop is connected directly or via safety unit at the 638 X11).
Additional Minimal request of safety function by Cat. 3 and PL e
The category 3 and PL e can only be attained if the STO-power on test is enabled.
The STO-power on test needs low-level at both STO# inputs by switch on the 24V control voltage.
The drive can not activate if one or both STO-inputs have high-level.
The function must configure in the Safety-Dialog parameter 2 (default Active).
These minimal requests are necessary to detect a failure. Failure detection is only possible if the safety
function is activated.
Both measures could execute by a PLC.
Example Function
Protection Level
EN 954-1 ISO 13849-1
Application Example 1 Safety door monitoring or emergency shut-
down with protection monitoring switch
Cat. 3 PL e
Application Example 2 Safety door monitoring or emergency shut-
down with protection monitoring switch and
time delay
Cat. 3 PL e
Application Example 3 Safety door monitoring or emergency shut-
down WITHOUT protection monitoring
switch
Cat. 3 PL d
Application Example 4 Safety door monitoring or emergency shut-
down with protection monitoring switch and
time delay of several drives
Cat. 3 PL e
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