ABB ACS880-04F-504A-3, Hardware Manual

Page: 181 / 202

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. 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.
• The Safe torque off function is ineffective against deliberate sabotage or misuse.
• The Safe torque off function has been designed to reduce the recognized
hazardous conditions. In spite of this, it is not always possible to eliminate all
potential hazards. The assembler of the machine must inform the final user about
the residual risks.
The Safe torque off function 181