422 Appendix: Safe torque off (STO)Operation principle1. The Safe torque off activates (the activation switch is opened, or safety relaycontacts open).2. The STO inputs IN1 and IN2 on the drive control board de-energize.3. The STO cuts off the control voltage from the drive IGBTs.4. The control program generates an indication as defined by parameter 3025 STOOPERATION.The parameter selects which indications are given when one or both Safe torqueoff (STO) signals are switched off or lost. The indications also depend on whetherthe drive is running or stopped when this occurs.Note: This parameter does not affect the operation of the STO function itself. TheSTO function will operate regardless of the setting of this parameter: a runningdrive will stop upon removal of one or both STO signals, and will not start untilboth STO signals are restored and all faults reset.Note: The loss of only one STO signal always generates a fault as it is interpretedas a malfunction of STO hardware or wiring.5. Motor coasts to a stop (if running). The drive cannot restart while the activationswitch or safety relay contacts are open. After the contacts close, a new startcommand is required to start the drive.Start-up including acceptance testTo ensure the safe operation of a safety function, validation is required. The finalassembler of the machine must validate the function by performing an acceptancetest. The acceptance test must be performed• at initial start-up of the safety function• after any changes related to the safety function (circuit boards, wiring,components, settings, etc.)• after any maintenance work related to the safety function. CompetenceThe acceptance test of the safety function must be carried out by a competent personwith adequate expertise and knowledge of the safety function as well as functionalsafety, as required by IEC 61508-1 clause 6. The test procedures and report must bedocumented and signed by this person. Acceptance test reportsYou must store the signed acceptance test reports in the logbook of the machine. Thereport must include documentation of start-up activities and test results, references to
