the drive or the motor can only be carried out after isolating the drive system fromthe main supply.WARNING!(With permanent magnet or synchronous reluctance [SynRM] motors only) In caseof a multiple IGBT power semiconductor failure, the drive system can produce analignment torque which maximally rotates the motor shaft by 180/p (with permanentmagnet motors) degrees regardless of the activation of the Safe torque off function.p denotes the number of pole pairs.Note:• If a running drive is stopped by using the Safe torque off function, the drive will cut offthe motor supply voltage and the motor will coast to a stop. If this causes danger or isnot otherwise acceptable, stop the drive and machinery using the appropriate stop modebefore 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 hazardousconditions. 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.MaintenanceAfter the operation of the circuit is validated at start-up, the STO function shall be maintainedby periodic proof testing. In high demand mode of operation, the maximum proof test intervalis 20 years. In low demand mode of operation, the maximum proof test interval is 2 years,see section Safety data (SIL, PL) (page 232). It is assumed that all dangerous failures of theSTO circuit are detected by the proof test. To perform the proof test, do the procedure insection Acceptance test procedure (page 229).Note:See also the Recommendation of Use CNB/M/11.050 (published by the Europeanco-ordination of Notified Bodies) concerning dual-channel safety-related systems withelectromechanical outputs:• When the safety integrity requirement for the safety function is SIL 3 or PL e (cat. 3 or4), the proof test for the function must be performed at least every month.• When the safety integrity requirement for the safety function is SIL 2 (HFT = 1) or PL d(cat. 3), the proof test for the function must be performed at least every 12 months.The STO function of the drive does not contain any electromechanical components.In addition to proof testing, it is a good practice to check the operation of the function whenother maintenance procedures are carried out on the machinery.Include the Safe torque off operation test described above in the routine maintenanceprogram of the machinery that the inverter runs.If any wiring or component change is needed after start up, or the parameters are restored,follow the test given in section Acceptance test procedure (page 229).Use only ABB approved spare parts.Record all maintenance and proof test activities in the machine logbook.Safe torque off function 231
