Operating manual
cyber
®
dynamic system
en-42
Doc. no.: 5022-D056658
Revision: 01
11 STO safety function instructions
The STO safety function (
S
afe
T
orque
O
ff) is used for safe torque shutdown and to reliably
protect drives from restarting. The drive system is fitted with a two-channel STO function
as standard in the basic model.
Advantages of the STO safety function:
-
Intermediate circuit and main circuit can remain active
-
No contact wear because only control voltages are switched on and off
-
Less wiring required
-
Single-channel or two-channel control possible
-
SIL 2 or SIL 3 systems possible
The STO safety function equates to stop category 0 (uncontrolled stoppage) defined
by EN 60204-1. The STO safety function of the server amplifier can be triggered by external
safety relays or by an external safety control with safe outputs.
The circuit design has been tested and subsequently assessed by TÜV. According to that
assessment, the circuit design used for the
“Safe Torque Off” safety function in the cyber
®
dynamic system series drive systems are suitable for meeting the requirements for SIL 3
in accordance with EN 61508 and category 4 PLe in accordance with EN ISO 13849-1:2015.
11.1 Important information for STO
If the STO function is actuated during operation, the drive will coast
to a stop in an uncontrolled manner and the drive system reports
the
“Error_amp_sto_active” fault. Controlled braking of the drive
will not be possible.
If an application requires controlled braking before the use of STO,
the drive must first be braked under control and then the STO
function must be triggered with a time delay.
Danger from short-term limited movements when STO function
is activated.
Simultaneous breakdown of two power transistors in the output stage
can cause short-term movement up to 180° / pole pair number of the
drive system.
Make sure that a limited movement of this kind cannot cause any
damage.
11.2 Intended use of STO
The STO function is designed only for functionally safe switching of a drive to torque OFF and
to prevent restarting. In order to achieve functional safety, the wiring of the safety circuit must
meet the safety requirements of EN 60204, EN 12100, EN 61508 and/or EN 13849-1
