ABB ACS880-17, Hardware Manual

Page: 230 / 244

230 The Safe torque off function
Use
1. Open the activation switch, or activate the safety functionality that is wired to the STO
connection.
2. STO inputs on the inverter control unit [A41] de-energize, and the inverter control unit
cuts off the control voltage from the inverter 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 drive. Therefore maintenance work on
electrical parts of the drive or the motor can only be carried out after isolating the
drive from the main supply.
Stop the inverter (if running), switch the input power off and isolate the drive from the power line by a
disconnector.
Check the Safe torque off circuit connections against the wiring diagram.
Close the disconnector and switch the power on.
Test the operation of the STO function when the motor is stopped.
• Give a stop command to the inverter (if running) and wait until the motor shaft is at a standstill.
Ensure that the inverter operates as follows:
• Open the STO circuit. The inverter generates an indication if one is defined for ‘stopped’ state in
parameter 31.22 (see the firmware manual).
• Give a start command to verify that the STO function blocks the inverter’s operation. The motor
should not start.
• Close the STO circuit.
• Reset any active faults. Restart the inverter and check that the motor runs normally.
Test the operation of the STO function when the motor is running.
• Start the inverter and ensure the motor is running.
• Open the STO circuit. The motor should stop. The inverter generates an indication if one is defined
for ‘running’ state in parameter 31.22 (see the firmware manual).
• Reset any active faults and try to start the inverter.
• Ensure that the motor stays at a standstill and the inverter operates as described above in testing
the operation when the motor is stopped.
• Close the STO circuit.
• Reset any active faults. Restart the inverter and check that the motor runs normally.
Document and sign the acceptance test report which verifies that the safety function is safe and
accepted for operation.
Action