24VDC safety relay
Match the safety relay model, reset logic, contact rating, and safety-category design before replacement.
$35-$250
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ABB VFD Fault 5010 - Safe Torque Off Meaning
Fault 5010 on ABB ACS drives (ACS580, ACS880, ACH580) indicates that the Safe Torque Off (STO) function has been activated. STO is a safety function per IEC 61800-5-2 that removes the gate drive signals from the output IGBTs, preventing the drive from producing torque without removing main power from the drive. Fault 5010 means the STO circuit has interrupted motor output, either intentionally (safety system request) or due to a wiring or component problem.
Common Causes
- Safety relay or safety PLC opened the STO circuit: The most common cause is intentional. An e-stop button, light curtain, safety mat, or safety relay opened the STO input circuit as designed.
- Loose or broken STO wiring: The STO inputs on ABB drives (terminals STO1+ / STO1- and STO2+ / STO2- on ACS880, or the STO connector on smaller drives) are 24VDC logic signals. A loose wire or connector vibration causes an unintended STO trip.
- Failed safety relay or STO card: The safety relay supplying the STO signal can fail in the open state, permanently activating STO. On ACS880 drives with an STO option card, the card itself can fail.
- Power supply to STO circuit lost: The 24VDC supply powering the safety relay or STO logic is required; loss of this supply removes the STO enable signal.
Step-by-Step Fix
- Identify why the STO was activated. Check the machine’s safety system. If an e-stop or guard door is open, close it and reset the safety relay before attempting to restart the drive.
- Check STO input wiring. With drive control power on (main power off), verify 24VDC is present on the STO input terminals (STO1+ and STO2+ on ACS880). No voltage = safety relay de-energized or wiring fault.
- Inspect STO circuit wiring. Trace the wiring from the safety relay output to the drive STO inputs. Look for broken conductors, damaged insulation, or loose terminal connections.
- Test the 24VDC safety supply. Confirm the 24VDC power supply feeding the safety relay is operational. Replace if output voltage is absent or out of tolerance (should be 22-26VDC).
- Reset the drive. After correcting the STO condition, perform a fault reset on the drive (via keypad or digital input). If STO has cleared, the drive should be ready to run.
Parts Often Needed
| Part | Notes |
|---|---|
| Safety relay (24VDC) | Match safety relay series (Pilz, Schmersal, Sick, etc.) |
| ABB STO option card (FSIO) | ACS880 drives with separate STO option module |
| 24VDC control power supply | Replace if STO supply is failed |
| STO wiring (24VDC, shielded) | Replace any damaged conductors in the STO circuit |
Service-Safe Parts Note
Do not buy parts to bypass STO. Price replacement safety relays, 24VDC supplies, wiring, or ABB STO modules only after a qualified technician identifies the failed component and confirms the safety circuit design. If you need outside help, start with repair options instead of changing the safety circuit blindly.
When to Call a Pro
Modifying or bypassing STO safety circuits is a machinery safety violation and must never be done to get a machine running. Fault 5010 without an obvious safety trigger requires a certified safety engineer and/or ABB service technician to diagnose the STO circuit.