SIEMENS
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Siemens PM 21 · 2017
Safety Integrated
Overview
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Function
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Safely Limited Speed (SLS)
The SLS function monitors the drive to ensure that it does not
exceed a preset speed or velocity limit.
Effect
The SLS function monitors the drive against a parameterized
speed limit. Four different limit values can be selected. As in the
case of SOS, the speed setpoint is not influenced independently.
After SLS has been selected, the higher-level control must bring
the drive down below the selected speed limit within a parame-
terizable time. If the speed limit is exceeded, a customizable
drive-integrated fault reaction occurs.
A factor can be applied to SLS limit 1 that is transferred over
PROFIsafe in 16-bit resolution. This allows an almost unlimited
number of limits to be specified.
Note:
This function is not available for SINAMICS S110.
Application
The SLS function is used if people are in the danger zone of a
machine and their safety can only be guaranteed by reduced
speed. Typical application cases include those in which an
operator must enter the danger zone of the machine for the pur-
poses of maintenance or setting up, such as a winder in which
the material is manually threaded by the operator. To prevent
injury to the operator, the roller may only spin at a safe reduced
speed. SLS is often also used as part of a two-stage safety con-
cept. While a person is in a less critical zone, the SLS function is
activated, and the drives are only stopped in a smaller area with
higher potential risk. SLS can be used not only for operator
protection, but also for machinery protection, e.g. if a maximum
speed must not be exceeded.
Customer benefits
The SLS function can contribute to a significant reduction in
downtime, or greatly simplify or even accelerate setup. The over-
all effect achieved is a higher availability of the machine. More-
over, external components such as speed monitors can be
omitted.
Safe Speed Monitor (SSM)
The SSM function warns when a drive is working below an ad-
justable speed limit. As long as it remains below the threshold,
the function issues a safety-related signal.
Effect
If a speed value drops below a parameterized limit, a safety-
related signal is generated. This can, for example, be processed
in a safety controller to respond to the event by programming,
depending on the situation.
Application
With the SSM function, in the simplest case, a safety door can be
unlocked if the speed drops below a non-critical level. Another
typical example is that of a centrifuge that may be filled only
when it is operating below a configured speed limit.
Customer benefits
Unlike SLS, there is no drive-integrated fault reaction when the
speed limit is exceeded. The safe feedback can be evaluated in
a safety controller, allowing the user to respond appropriately to
the situation.
Safe Direction (SDI)
The SDI function ensures that the drive can only move in the se-
lected direction.
Effect
A deviation from the direction of motion currently being moni-
tored is detected reliably and the configured drive-integrated
fault reaction is initiated. It is possible to select which direction
of rotation is to be monitored.
Application
The SDI function is used when the drive may only move in one
direction. A typical application is to make a danger area acces-
sible to the operator, provided the machine is moving in the safe
direction, i.e. away from the operator. In this status, the operator
can safely feed material into or remove it from the working area.
Customer benefits
The function saves the use of external components such as
speed monitors and the associated wiring. The release of a dan-
ger zone while the machine is moving away from the operator
increases productivity. Without the SDI function, the machine
would have to be stopped safely while material is fed in or
removed.
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© Siemens AG 2017