What would cause the Altivar ATV340 Process Drive to power up with STO on the display?
Resolution:
The STO (Safe Torque Off) indication appears when the drive's safety inputs are not receiving the required 24 VDC signal.
The ATV340 safety function requires 24 VDC to be present on both the STOA and STOB terminals. If these terminals are not wired to an external safety circuit, a jumper must be installed (or left in place) between 24 VDC and STOA/STOB at the CN2 connector on top of the drive.
If the required 24 VDC signal is missing, the drive will remain in the STO state and will not operate.
Troubleshooting Checklist
- Verify that 24 VDC is present at the STOA and STOB terminals.
- Check all safety circuit wiring for loose or incorrect connections.
- Confirm that the CN2 jumper is installed if no external safety device is connected.
- Inspect any connected safety relays or safety controllers for proper operation.
If this article does not answer your question, check out our FAQ database that has answers to more commonly asked questions:
Frequently Asked Questions - Schneider Electric (se.com)
If this FAQ did not solve your issue, you can call us at 1-888-778-2733 Option 2 and then 4 or e-mail us atdrive.products.support@se.comto create a case with our Technical Support Team.
If you are not located in North America, please contact your local Customer Care Center for assistance:
Released for: Schneider Electric Canada
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