Safe torque off 1

What does FA81 mean?

An asymmetric loss of one of the Safe Torque Off (STO) signals has occurred (e.g., IN1 lost while IN2 is present). This is interpreted as a malfunction in the safety circuit and causes the drive to trip. The drive will not start until both STO signals are restored and all related faults are reset.

• Open circuit or wiring break specifically affecting the STO IN1 input signal cable.
• Faulty safety relay or PLC output module that controls STO IN1, causing it to drop out independently.
• Loose connection or faulty terminal (e.g., STO_IN1 terminal) on the drive's safety board.
• Internal component failure on the drive's STO circuit for the IN1 channel.
• Incorrect voltage level on STO IN1 (e.g., below 18VDC) while STO IN2 remains high (e.g., 24VDC).

Click steps to track your progress.

1. 1

   De-energize the drive. Measure continuity of the STO IN1 cable conductor from the safety source (relay/PLC) to the drive's STO IN1 terminal.

2. 2

   Measure voltage across the STO IN1 terminal (e.g., X1) relative to common (e.g., X3) with the safety function engaged; expect 24VDC.

3. 3

   Verify the output status of the safety relay or PLC module driving STO IN1, ensuring it provides a consistent signal when active.

4. 4

   Inspect the wiring at the drive's STO IN1 terminal (e.g., X1) for loose connections, damage, or corrosion.

5. 5

   If a separate safety module is used, check its diagnostic LEDs or software status for faults related to STO channel 1.