What causes fault code VFD-OC3 (VFD Overcurrent — Steady State)?

Mechanical load increased suddenly — product pileup, bearing failure, or process change. Motor winding insulation degrading — intermittent phase-to-phase short under load. VFD output cable damaged — insulation breakdown in conduit, especially at sharp bends or pull points. Ambient temperature too high — VFD derating due to enclosure temperature above 40C/104F. IGBT module degrading — one leg conducting more than others

How do I fix fault code VFD-OC3?

Monitor output current on VFD display during operation — compare to motor FLA. Check motor temperature with IR thermometer — compare all three phases at motor junction box. Megger VFD output cable from drive terminals to motor — disconnect both ends first. Check enclosure ambient temperature — install ventilation fan if above 40C. Compare all three output phase currents with clamp meter — more than 5% imbalance indicates motor or cable issue. If current is normal but fault persists, VFD current sensing board or CT may be faulty

VFD Overcurrent — Steady State

VFD-OC3

Drive tripped on overcurrent while running at constant speed. Current exceeded trip threshold during normal operation, not during accel or decel.

high vfd conveyor packaging palletizer

vfd overcurrent steady-state motor winding

Probable Causes (ranked)

Mechanical load increased suddenly — product pileup, bearing failure, or process change
Motor winding insulation degrading — intermittent phase-to-phase short under load
VFD output cable damaged — insulation breakdown in conduit, especially at sharp bends or pull points
Ambient temperature too high — VFD derating due to enclosure temperature above 40C/104F
IGBT module degrading — one leg conducting more than others

Fix Steps

1 Monitor output current on VFD display during operation — compare to motor FLA
2 Check motor temperature with IR thermometer — compare all three phases at motor junction box
3 Megger VFD output cable from drive terminals to motor — disconnect both ends first
4 Check enclosure ambient temperature — install ventilation fan if above 40C
5 Compare all three output phase currents with clamp meter — more than 5% imbalance indicates motor or cable issue
6 If current is normal but fault persists, VFD current sensing board or CT may be faulty

Field Trick

Clamp all three motor leads through a single CT window — if the reading is not zero, you have a ground fault. On a healthy motor with balanced phases, the vector sum of all three phases is zero.

Suggested Replacement Parts

Parts matched to fault category: Vfd

Allen-Bradley PowerFlex 525 AC Drive 1HP P/N: 25B-D2P3N114 1HP, 480V, 3-phase, built-in EtherNet/IP, EMC filter

AutomationDirect $395.00 Amazon $450.00 Grainger $520.00

ABB ACS580 General Purpose Drive 2HP P/N: ACS580-01-05A7-4 2HP, 480V, built-in safe torque off, adaptive programming

AutomationDirect $425.00 Amazon $480.00 Grainger $550.00

GS20 AC Drive 1HP (Budget Option) P/N: GS20-20P5 1HP, 230V, sensorless vector, compact size — good replacement for testing

AutomationDirect $149.00 Amazon $175.00

Prices are estimates. Verify part numbers match your equipment before ordering.

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