Technical data

Safety Integrated Functions
8.3 System features
Function Manual
Function Manual, 06/2012, 6SL3097-4AB10-0BP4
353
WARNING
• Violation of limits may briefly lead to a speed higher than the speed setpoint, or the axis
may pass the defined position to a certain extent, depending on the dynamic response
of the drive and on parameter settings.
• Mechanical forces greater than the maximum drive torque may force a drive currently
operated in position control mode out of the Safe Operating Stop state (SOS) and
trigger stop function category 1 in accordance with EN 60204-1 (fault reaction function
STOP B).
WARNING
Within a single-encoder system:
a) a single electrical fault in the encoder
b) a broken encoder shaft (or loose encoder shaft coupling), or a loose encoder housing will
cause the encoder signals to remain static (that is, they no longer follow a movement while
still returning a correct level), therefore preventing a fault from being detected while the
drive is in a stop state (for example, drive in SOS state).
Generally, the drive is held by the active closed-loop control. With closed loop control, it is
conceivable that vertical (suspended) drives in particular can move without their motion
being detected.
The risk of an electrical fault in the encoder as described under a) is only present for few
encoder types employing a specific principal of operation (for example, encoders with
microprocessor controlled signal generation such as the Heidenhain EQI, Hübner HEAG
159/160, or AMO measuring systems with sin/cos signals).
The risk analysis of the machine manufacturer must include all of the faults described
above. Additional safety measures have to be taken for drives with suspended/vertical or
dragging loads in order to exclude the faults described in a). For example:
• Use of an encoder with analog signal generation
In order to exclude the fault described in b), for example:
• Perform an FMEA regarding encoder shaft breakage (or slip of the encoder shaft
coupling), and implement a solution to prevent loose encoder housings, integration of a
fault exclusion process - for example according to IEC 61800-5-2