Safety functions integrated in the drive
5.1 Basic safety information
F-TM ServoDrive
38 Equipment Manual, 02/2020, A5E47579503-AA
Hardware STO
The F-TM ServoDrive internally monitors the fail-safe digital input at STO+ and STO-
terminals for discrepancies.
Discrepancy monitoring
Due to the design of the Hardware STO circuit, a discrepancy cannot occur at STO+ and
STO- terminals. As long as the STO terminal is de-energized, STO is selected. The
Hardware STO signal is read in internally via two channels.
To comply with the requirements for timely error detection from EN 61800-5-2, the switch-off
signal paths of the end stage in both monitoring channels are also cyclically tested. Errors
when testing the shutdown paths trigger STO. A manual forced checking procedure (test
stop) for testing the shutdown paths of the F-TM ServoDrive is therefore not needed.
Forced checking procedure
You should nevertheless examine its necessity for diagnosing the utilized sensors or for
performing a test stop in the context of the overall system.
5.1.5 Overview of the Safety Integrated functions
Compared to standard drive functions, safety functions have an especially low error rate.
Performance Level (PL) and Safety Integrity Level (SIL) as defined in the corresponding
standards are a measure for the error rate.
For this reason, safety functions are suitable for use and for risk reduction in safety-related
applications. An application is safety-related when the risk analysis of the machine or plant
has identified a particular risk potential in the application.
Safety Integrated means that the safety functions are integrated in the drive and can be
executed without additional external components.
Conformity of Safety Integrated functions
The Safety Integrated functions comply with:
● Safety Integrity Level (SIL) 2 according to IEC 61508 Part 1-3
● Category 3 according to ISO 13849-1
● Performance Level (PL) d according to ISO 13849-1
For functional safety of variable-speed drives, the standard IEC 61800-5-2, in which the
Safety Integrated functions are defined, applies.
Function groups
For the F-TM ServoDrive, the safety functions are divided into the following function groups:
● Safety Integrated stop function (hardware STO)
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