Powering up stopped due to "STO via Power Module terminals"

What does A01790 mean?

The inverter's automatic self-test during power-up was interrupted because the 'STO via Power Module terminals' function is active. This prevents the drive from completing its initialization and starting normally, indicating an unintended or misconfigured safety state at startup.

• The STO (Safe Torque Off) inputs on the Power Module (PM) terminals (e.g., X124/X125) are active (e.g., 0V, Open) at power-up, preventing drive initialization.
• External safety circuit or emergency stop relay is held in an active STO state, applying the STO signal to the drive.
• Faulty wiring or short circuit on the STO input terminals, causing a permanent STO active signal.
• Control Unit (CU) or Power Module (PM) hardware issue incorrectly interpreting the STO input state.

Click steps to track your progress.

1. 1

   1. Verify that the STO inputs on the Power Module terminals (e.g., X124/X125) are correctly wired and receiving a valid (e.g., 24VDC, Closed) signal at power-up.

2. 2

   2. Check the status of the external safety circuit or emergency stop system to ensure it is not unintentionally asserting the STO signal.

3. 3

   3. Measure the voltage level at the STO input terminals on the Power Module to confirm they are in a 'safe off' (e.g., 0V) state when they should be 'safe on' (e.g., 24VDC).

4. 4

   4. Deactivate and reactivate the STO inputs (e.g., cycle the safety relay) to clear any transient conditions.

5. 5

   5. Perform a cold start (power off, wait, power on) after ensuring the STO inputs are correctly released.