Use - ABB ACS880-104 Hardware Manual

324 The Safe torque off function

Use

1. Open the activation switch, or activate the safety functionality that is wired to the STO
connection.
2. The STO inputs on the inverter 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 (refer to
the firmware manual of the inverter).
4. The motor coasts to a stop (if running). The inverter will not restart while the activation
switch or safety relay contacts are open.
5. Deactivate the STO by closing the activation switch, or reseting 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 inverter. Therefore maintenance work on electrical parts
of the inverter or the motor can only be carried out after isolating the inverter 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!
(With permanent magnet or synchronous reluctance [SynRM] motors only)
In case of a multiple IGBT power semiconductor failure, the inverter 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 inverter is stopped by using the Safe torque off function, the inverter 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 inverter 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 inverter.
• 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.