STO hardware failure

What does 5090 mean?

A critical hardware failure has occurred within the Safe Torque Off (STO) circuit of the drive, compromising safety functionality. This means the drive cannot guarantee safe disconnection of motor torque, requiring specialist intervention to ensure safety integrity.

• Internal hardware fault within the drive's Safe Torque Off (STO) circuit (e.g., relay, semiconductor switch).
• Failure of an external safety relay or safety input to the drive, preventing proper STO circuit activation/deactivation.
• Damage to the safety input wiring (e.g., short to ground, open circuit) to drive terminals STO1/STO2.
• Power supply issue to the STO circuit (e.g., low voltage on STO supply terminal).
• Incorrect configuration of internal safety parameters (P6-80, P6-81) for the STO function.

Click steps to track your progress.

1. 1

   Power cycle the drive. Observe the status of the STO LEDs on the drive (e.g., STO1/STO2 green).

2. 2

   Verify the integrity of the external safety circuit and its connections to the drive's STO input terminals (e.g., STO1, STO2).

3. 3

   Measure the voltage levels at the drive's STO input terminals (e.g., 24VDC when active, 0VDC when inactive).

4. 4

   Perform a functional test of the STO circuit according to the drive's safety manual, ensuring motor torque removal.

5. 5

   If an internal fault is suspected after external checks, contact authorized service for internal hardware diagnosis.