Issue:
STO on AT600 and ATV900 Drives.
Product Line:
Altivar Process Drives
Environment:
All
Cause:
NA
Resolution:
STO is not a fault code. It is a state of the drive. It means that Safe Torque Off function is active. The drive is not detecting 24Vdc on the STOA or STOB terminals.
Measure for 24Vdc between +24 to COM to verify the internal power supply. If you don't have 24 Vdc present on the +24 terminal, measure DC voltage between PA+ and PC- to check your DC bus voltage.
Confirm that the factory installed jumper between +24 to STOA & STOB is solidly connected. The jumper is removed if a safety circuit is installed. Verify continuity of the safety circuit (if installed).
Make sure the Sink/Source switch is in the Source position.
When the voltage on STOA and STOB is re-established, the drive status will return to RDY if there is not an active run command, or NST if a run command is active. To clear NST, remove the run command.
STO on AT600 and ATV900 Drives.
Product Line:
Altivar Process Drives
Environment:
All
Cause:
NA
Resolution:
STO is not a fault code. It is a state of the drive. It means that Safe Torque Off function is active. The drive is not detecting 24Vdc on the STOA or STOB terminals.
Measure for 24Vdc between +24 to COM to verify the internal power supply. If you don't have 24 Vdc present on the +24 terminal, measure DC voltage between PA+ and PC- to check your DC bus voltage.
Confirm that the factory installed jumper between +24 to STOA & STOB is solidly connected. The jumper is removed if a safety circuit is installed. Verify continuity of the safety circuit (if installed).
Make sure the Sink/Source switch is in the Source position.
When the voltage on STOA and STOB is re-established, the drive status will return to RDY if there is not an active run command, or NST if a run command is active. To clear NST, remove the run command.
Released for:Schneider Electric India
