Qualified persons only. This page is general education, not a procedure. Work on electrical or mechanical equipment only if you are trained, authorized and qualified for that equipment. Follow your employer's written energy-control program under OSHA 29 CFR 1910.147, the electrical safe-work practices in NFPA 70E, and the equipment manufacturer's manual. If you are unsure, stop and ask a qualified person.
Drive capacitors stay charged after power is removed. Follow the drive manufacturer's stated wait time and verify absence of voltage on the DC bus with a properly rated meter before touching internal parts. Do not reset a drive repeatedly without finding the cause.
Step 0: Before you touch anything
- Read and write down the exact fault code and any fault history the keypad shows. Photograph the display.
- Find the drive's manual (model and series on the nameplate) and look up that exact code. Manufacturer fault tables are the authority, not this page.
- If the job requires opening the enclosure or touching the motor, conductors or load, apply lockout/tagout per your program first. See Lockout/tagout basics.
Common fault categories and what to check first (outside the drive)
Vendors name these differently. These categories are a general grouping; your manual's code list decides what a code means.
| Overcurrent | Mechanical jam or binding on the load, too-short acceleration time, motor or cable problem. Look at the load and recent changes first. |
|---|---|
| Overvoltage (DC bus) | Often during deceleration of a high-inertia load, or high incoming line voltage. Check decel time and whether a braking option is specified. |
| Undervoltage | Supply dip, a loose or open supply connection, or a blown supply fuse. Check upstream protection and supply. |
| Overload (motor or drive) | Load demand above rating for too long. Compare load to nameplate and the drive's motor settings. |
| Over-temperature | Blocked airflow, failed fan, dirty heat sink or filters, hot room. Look at cooling and the enclosure. |
| Ground fault | Insulation problem in motor or cable. Testing is a qualified-person job under lockout. |
| Input / output phase loss | Open phase upstream or between drive and motor. Check fuses, disconnects and terminations (de-energized). |
| Communication / fieldbus | Network cable, address or controller changes. Check what changed in the control system. |
| External fault / interlock | A permissive or safety input opened. Find which device opened and why. Never bypass an interlock or safety circuit. |
| Parameter / internal | Configuration changes or internal hardware faults. Use the manual and the manufacturer's support. |
When to stop and escalate
- Repeated trips after a reset, burning smell, visible damage, or a ground-fault code.
- Any check that would need work inside an energized enclosure. That requires an energized-work justification and controls under NFPA 70E, not a shortcut.
Free fault-code lookups and vendor references
- Industrial Automation Co. alarm/fault lookup
- ErrorCodeFixes VFD fault code lookup (multi-brand)
- Your drive manufacturer's manual library (search the manufacturer's site for your exact model).
Sources: OSHA 29 CFR 1910.147 (eCFR); NFPA 70E (nfpa.org); OSHA Control of Hazardous Energy. The categories above are a general summary; refer to the manufacturer for code meanings. Last reviewed 2026-10-16.