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Use
1.
Open the activation switch, or activate the safety functionality that is wired to the STO
connection.
2.
The STO inputs on the drive control unit de-energize, and the control unit cuts off the
control voltage from the output IGBTs.
3.
The control program generates an indication as defined by parameter 31.22 (see the
firmware manual of the drive).
4.
The motor coasts to a stop (if running). The drive will not restart while the activation
switch or safety relay contacts are open.
5.
Deactivate the STO by closing the activation switch, or resetting the safety functionality
that is wired to the STO connection.
6.
Reset any faults before restarting.
WARNING!
The Safe torque off function does not disconnect the voltage of the main and auxiliary
circuits from the drive. Therefore maintenance work on electrical parts of the drive
or the motor can only be carried out after isolating the drive from the supply and all
other voltage sources.
WARNING!
The Safe torque off functionality is only achieved through the XSTO connector of
the inverter control unit (A41). True Safe torque off functionality is not achieved
through the XSTO connectors of other control units (such as the supply control unit
or the brake control unit).
The Safe torque off function is supported by any ACS880 inverter or drive control
program. It is not supported by supply, DC/DC converter or brake firmware.
WARNING!
The drive cannot detect or memorize any changes in the STO circuitry when the
drive control unit is not powered. If both STO circuits are closed and a level-type
start signal is active when the power is restored, it is possible that the drive starts
without a fresh start command. Take this into account in the risk assessment of the
system.
WARNING!
(With permanent magnet or synchronous reluctance [SynRM] motors only)
In case of a multiple IGBT power semiconductor failure, the drive can produce an
alignment torque which maximally rotates the motor shaft by 180/p degrees (with
permanent magnet motors) or 180/2p degrees (with synchronous reluctance [SynRM]
motors) regardless of the activation of the Safe torque off function. p denotes the
number of pole pairs.
Notes:
•
If a running drive is stopped by using the Safe torque off function, the drive will cut off
the motor supply voltage and the motor will coast to a stop. If this causes danger or is
The Safe torque off function 227
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