144 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 drive control unit de-energize, and the drive 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 drive).
4. Motor coasts to 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 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 system from the main supply.
WARNING! (With permanent magnet or synchronous reluctance [SynRM] motors
only) In case of a multiple IGBT power semiconductor failure, the drive system
can produce an alignment torque which maximally rotates the motor shaft by
180/p (with permanent magnet motors) or 180/2p (with synchronous reluctance [SynRM]
motors) degrees regardless of the activation of the Safe torque off function. p denotes the
Close the disconnector and switch the power on.
Test the operation of the STO function when the motor is stopped.
• Give a stop command for the drive (if running) and wait until the motor shaft is at a standstill.
Make sure that the drive operates as follows:
• Open the STO circuit. The drive 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 drive operations. The motor should
not start.
• Close the STO circuit.
• Reset any active faults. Restart the drive and check that the motor runs normally.
Test the operation of the STO function when the motor is running:
• Start the drive and make sure the motor is running.
• Open the STO circuit. The motor should stop. The drive 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 drive.
• Make sure that the motor stays at standstill and the drive operates as described above in testing
the operation when the motor is stopped.
• Close the STO circuit.
• Reset any active faults. Restart the drive 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
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