3.7.4
Safely Limited Speed (SLS)
What is the effect of the SLS safety function?
The inverter with active SLS function monitors the motor speed. When the monitoring limit is
exceeded, the inverter stops the motor as quickly as possible.
As a consequence, the SLS function allows an electrically driven machine component to be
operated with a temporarily reduced speed or velocity that is not hazardous.
Table 3-6
An overview of the principle of operation of SLS, selected when the motor is rotating
Safely Limited Speed (SLS)
Standard inverter functions linked with SLS
1. The inverter identifies when SLS is selected via a fail-
safe input or via safety-related PROFIsafe communi‐
cation.
---
2. SLS allows a motor to reduce its possibly inadmissibly
high speed within a defined time – or to reduce it along
a defined braking ramp.
The inverter limits the speed setpoint to
values below the SLS monitoring.
If the motor rotates faster than the SLS
monitoring value, then the inverter brakes
the motor along the OFF3 ramp.
3. The inverter monitors the absolute actual speed
against the set SLS monitoring.
The inverter signals "SLS is active" via a fail-safe dig‐
ital output or via PROFIsafe.
If the motor speed exceeds the SLS monitoring, the
inverter responds with a "safe stop" and brakes the
motor as quickly as possible.
The inverter limits the speed setpoint to
values below the SLS monitoring.
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SLS
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Figure 3-5
Principle of operation of SLS
The SLS safety function is standardized
The SLS function is defined in IEC/EN 61800-5-2:
"The SLS function prevents the motor from exceeding the defined speed limit."
⇒ The SLS inverter function is in conformance with IEC/EN 61800-5-2.
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Description
3.7 An overview of the principle of operation of the safety functions
Safety Integrated - SINAMICS G110M, G120, G120C, G120D and SIMATIC ET 200pro FC-2
Function Manual, 01/2017, FW V4.7 SP6, A5E34261271B AD
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