Safe torque off

What does 5091 mean?

The Safe Torque Off (STO) function has been activated, removing power from the motor and preventing unintended starts. This fault indicates that the STO safety chain has been interrupted or a fault related to STO occurred, regardless of whether one or both signals were lost.

• Interruption or missing STO input signal (typically two channels, STO1 and STO2), indicating an activated safety function.
• Internal STO circuit fault within the drive's safety hardware.
• External safety device (e.g., E-stop, safety gate, light curtain) activated, causing the STO inputs to drop, removing motor torque.
• Wiring fault (e.g., broken wire, short circuit to ground) in the STO safety chain to the drive.

Click steps to track your progress.

1. 1

   Verify that all external safety devices (e.g., emergency stop buttons, safety gates, safety relays) in the STO circuit are in their safe operating state and not activated.

2. 2

   Check the STO input signals (typically digital inputs for STO1 and STO2) at the drive terminals for proper voltage levels (e.g., 24VDC when safe torque off is inactive).

3. 3

   Inspect the wiring of the STO safety chain for any breaks, loose connections, short circuits, or damage.

4. 4

   If applicable, test the functionality of external safety devices connected to the STO inputs to ensure they are operating correctly.

5. 5

   Refer to the drive's hardware manual for detailed information on STO wiring, signal specifications, and diagnostic indicators.