Challenge #5 · vfds
Ready, But It Won't Run
A conveyor VFD shows READY on the display, no fault. The PLC gives the run command. The drive just sits there and the motor never moves.
① Run your checks
② Make the call
③ Explain your reasoning optional
A strong answer covers:
- What you did: checked the drive's fault status, the run command at the run input, and the safety enable / STO input.
- The reason: READY with no fault and 24V at the run input means the drive and the command are fine; but the STO/enable read 0V, so the safety string is open.
- Determined outcome: a drive won't run with STO unsatisfied; trace the safety string for the open (guard door, safety relay, e-stop), don't condemn the drive.