166 The Safe torque off functionUse1. Open the activation switch, or activate the safety functionality that is wired to the STOconnection.2. STO inputs on the inverter control unit de-energize, and the inverter control unit cutsoff the control voltage from the inverter IGBTs.3. The control program generates an indication as defined by parameter 31.22 (refer tothe firmware manual of the inverter).4. The motor coasts to a stop (if running). The inverter will not restart while the activationswitch or safety relay contacts are open.5. Deactivate the STO by closing the activation switch, or reseting the safety functionalitythat is wired to the STO connection.6. Reset any faults before restarting.WARNING! The Safe torque off function does not disconnect the voltage of themain and auxiliary circuits from the inverter. Therefore maintenance work onelectrical parts of the inverter or the motor can only be carried out after isolatingthe inverter from the main supply.WARNING! The Safe torque off functionality is only achieved through the XSTOconnector of the inverter control unit. True Safe torque off functionality is notachieved through the XSTO connectors of other control units (such as the supplycontrol unit or the brake control unit).The Safe torque off function is supported by any ACS880 inverter or drive firmware. It isnot supported by supply or brake firmware.WARNING! (With permanent magnet or synchronous reluctance [SynRM] motorsonly) In case of a multiple IGBT power semiconductor failure, the inverter systemcan produce an alignment torque which maximally rotates the motor shaft by180/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 thenumber of pole pairs.Notes:• If a running inverter is stopped by using the Safe torque off function, the inverter willcut off the motor supply voltage and the motor will coast to a stop. If this causesdanger or is not otherwise acceptable, stop the inverter and machinery using theappropriate stop mode before activating the Safe torque off function.• The Safe torque off function overrides all other functions of the inverter unit.• 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.
