Sto Function; Overview - Eaton PowerXL DA1 Series Installation Manual

2 Engineering

2.10 STO function

2.10 STO function

2.10.1 Overview

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DA1 variable frequency drives include theSTO function (STO =Safe Torque
Off) as part of their standard range of functionalities. This function meets the
requirements for variable-speed drive systems defined in Part 5-2 of the
IEC 61800 standard and ensures that torque-generating energy is no longer
able to act on the motor shaft and that unintended starting is prevented.
Moreover, this state is monitored internally in the drive.
The STO function can be used anywhere where the corresponding motor will
come to a stop by itself in a sufficiently short amount of time as a result of
the corresponding load torque or friction, as well as in cases in which
coasting has no safety implications.
v
t1
Figure 39: STO conforming to Stop Category 0
￫
This safety function corresponds to uncontrolled stopping as
defined in IEC 60204-1, Stop Category 0.
It can be used if it is necessary to switch off the power in order
to prevent unexpected starts.
Additional measures (such as mechanical brakes) may be
required in order to prevent hazards in which external factors
are involved (e. g., suspended loads falling down).
￫
Application examples can be found in the Eaton safety manual
PU05907001Z.
You can find the safety manual as a PDF document on the
Eaton website at the following address:
http://www.eaton.eu/Europe/Electrical/CustomerSupport/TechnicalLiterature/SafetyManual/index.htm
DA1 Variable Frequency Drives 08/18 MN04020005Z-EN www.eaton.com
v = Motor speed
t1 = STO shutdown
Start of coasting
Gray = Coasting time for motor
without safety implications
t