S700 Safety Guide | 2 English
2.4.11 Safe Torque Off (STO)
The STO safety implementation on the is certified. The safety circuit concept for realizing the
safety function "Safe Torque Off" in the servo amplifiers S700 is suited for SIL CL3 according
to IEC 62061 and PLe according to ISO 13849-1.
The STO safety function corresponds to stop category 0 (uncontrolled stopping) acc. to
EN60204-1. The safety function STO can be operated from external safety switch gears
(relays), from a safe external control (semiconductor output or driven contact) or from the
built-in safety card S1-2 or S2-2
SIL2 / PLd solutions can be implemented with single-channel or dual-channel control with
simple safety switching devices.
A SIL3 / PLe solution requires a safety control that periodically tests the safe switching of
the pulse inhibitor by analyzing the feedback signal.
2.4.11.1 Safety instructions
WARNING
No Brake Power
Serious injury could result when a suspended load is not properly blocked.
The servo amplifier cannot hold a vertical load when STO is active.
Add a safe mechanical blocking (for instance, a motor-holding brake).
CAUTION
High electrical voltage
Risk of electrical shock! The STO function does not provide an electrical
separation from the power output. If access to the motor power terminals is
necessary,
disconnected the servo amplifier from mains supply,
consider the discharging time of the DC-Bus link.
In case of single channel control: If the STO is automatically activated by a control system,
then make sure that the output of the control is supervised for possible malfunction. This can
be used to prevent a faulty output from unintentionally activating the function STO. Since
STO is used in a single-channel system, erroneous engaging will not be recognized.
When STO is engaged during operation, the motor runs down out of control and the servo
amplifier displays the error F27. If a controlled braking before the use of STO is necessary,
the drive must be braked and the inputs STO1-ENABLE and STO2-Enable have to be sep-
arated from +24 VDC time-delayed.
When wiring the STO input within one enclosure it must be paid attention to the fact that the
used cables and the enclosure meet the requirements of IEC 60204-1. If the wiring leads out-
side the demanded enclosure, the cables must be laid durably (firmly), and protected from
outside damage.
If the STO function is not needed in the application, then the inputs STO1-ENABLE and
STO2-Enable must be connected directly with +24VDC. The servo amplifier cannot be used
as a safety component referring to the EC Machine Directive now.
58 Kollmorgen | wiki-kollmorgen.eu | February 2017
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