Eaton PowerXL DA1 - STO Function; Overview

2 Engineering
2.10 STO function
DA1 Variable Frequency Drives 11/16 MN04020005Z-EN www.eaton.com 59
2.10 STO function
2.10.1 Overview
DA1 variable frequency drives include the STO 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 = Motor speed
t1 = STO shutdown
Start of coasting
Gray = Coasting time for motor
without safety implications
Figure 33:: 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).
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CAUTION
When used in conjunction with permanent magnet motors and
in the unlikely case of multiple output semiconductors (IGBTs)
failing, having the STO function activated may result in a motor
shaft rotational movement of 180 degrees/p (p = Number of
motor pole pairs).
t
t1
v