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05.01
9.3Safety of machinery – safety–related parts of controls according to EN ISO 13849–1:2008
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Siemens AG 2012 All Rights Reserved
SIMODRIVE 611 Configuration Manual (PJU) – 02/2012 Edition
9.3
Safety of machinery – safety–related parts of controls
according to EN ISO 13849–1:2008
9.3.1
General information
With the introduction of EN 62061 and EN ISO 13849–1 as successor to the EN
945–1 standard, several things have changed regarding the assessment of
suitable safety technology. Not only is the structure of a safety–related circuit
taken into consideration, as was previously the case according to EN 954–1,
but beyond this, the performance of the safety technology is also assessed
along with the reliability; and if necessary, the software and many other related
issues.
9.3.2
Safety–related stop functions of electric drive systems accor-
ding to DIN EN 61800–5–2
Safety function STO – Safe Torque Off
The Safe Torque Off (STO) function is a safety function to avoid unexpected
starting. This function prevents the unexpected starting of a motor, connected to
the drive control unit, from standstill. When the Safe Torque Off function is acti-
vated, the motor shaft cannot generate a torque.
This safety function should only be activated after the drive has come to a
standstill, otherwise it loses its braking capability.
The standstill of the drive as well as the activation of the Safe Torque Off func-
tion must be realized and secured using an external machine control. If the
drive is at a standstill and the Safe Torque Off function is active, additional bra-
kes may be required for dangers due to the fact that the drive shaft is subject to
an external torque.
For SIMODRIVE 611, the Safe Torque Off function is a ”Device to shut down
and avoid unexpected starting” according to EN 60204–1 Section 5.4. This be-
havior corresponds to stop Category 0, according to EN 60204–1:2006.
There is no electrical isolation from the line supply with the Safe Torque Off
function. As a consequence, this function does not represent a protective
device against electric shock.
Safety function SS1 – safe stop (time controlled)
Initiates that the motor decelerates, and after an application–specific delay, in-
itiates the STO function.
This behavior corresponds to stop Category 1, according to EN 60204–1:2006.
Function
Activation
Function
9 Cabinet Design and EMC
02.12
