Siemens SINAMICS G130 Engineering Manual page 257

According to IEC 61508, IEC 62061 and ISO 13849-1 it is required to quantify the probability of failures for safety
functions in form of a PFH value (Probability of Failure per Hour). The PFH value of a safety function depends on the
safety concept of the drive unit, its hardware configuration and on the PFH values of additional components, which
are required for the safety function. For SINAMICS units PFH values are provided in dependency on the hardware
configuration (number of units, number of sensors, etc.). Thereby no differece is made between the individual
integrated safety functions.
A list of certified components and firmware versions as well as a list of the PFH values are available on request.
This information is also contained in the Safety Evaluation Tool which is available on the Internet.
Functional safety
The Safe Torque Off function prevents the connected motor from starting accidentally from standstill or, in other
words, ensures the torque-free state of a rotating drive. A rotating axis loses its ability to brake.
However, the STO function does not isolate the installation from the supply system and it does not therefore provide
any protection against "electric shock".
During interruptions of operation or when the electrical installation is undergoing maintenance, repair or cleaning, it
must be completely isolated from the mains supply by means of the main breaker.
When STO is activated, asynchronous motors cannot rotate, even if several faults occur at the same time, because
the motor is completely de-magnetized.
In applications with permanent-magnet synchronous motors, e.g. of type 1FT6 or 1FK6, the permanent magnetization
means that limited movement might occur under specific boundary conditions when more than one fault is present.
Potential fault: Simultaneous breakdown of one power semiconductor in the upper inverter bridge and another one in
the lower bridge ("positive arm" and "negative arm").
Maximum residual movement:
§ With rotating synchronous motors:
§ With synchronous linear motors, the maximum movement corresponds to the pole width.
In order to assess the potential hazard posed by critical residual movements, the machine manufacturer must
perform a safety evaluation.
With respect to permanent-magnet synchronous motors such as SIMOTICS HT series HT-direct 1FW4 motors,
please note that voltage is present at the motor terminals when the rotor is turning as a result of the permanent
magnetization. If the motors are driven passively, voltage is induced in the motor even when STO or SS1 is activated.
Separate protective devices are recommended for these cases.
General Engineering Information for SINAMICS
360
a
=
max
Pole number
SINAMICS Engineering Manual – November 2015
Engineering Information
°
e.g.,1FT6, 6-pole motor;
of motor
Ó Siemens AG
a = 60 °
max
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