ABB ACS180-04S-03A7-1, Hardware Manual, Page: 172 / 192

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 drive cannot detect or memorize any changes in the STO circuitry when
the drive control unit is not powered or when the main power to the drive is
off. 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!
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 180/2 p 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 not otherwise acceptable, stop the drive and machinery
using the appropriate stop mode before activating the Safe torque off function.
• The Safe torque off function overrides all other functions of the drive.
172 The Safe torque off function