Cause : STO Loss 1 comes when STO1 and SCM1 short circuit lines are not connected. STO is a safety function designed to prevent unexpected motor operation and ensure personnel safety when working on machinery.

The STL1 fault in Delta MS300 drive indicates a Safe Torque Off (STO) Loss on channel 1. STO is a safety function designed to prevent unexpected motor rotation and potential hazards.

1. Check if the PIN of the IO card is broken.
2. Check if the IO card connects to the control board correctly, and if the screws are tightened well.