Overcurrent and overload faults are two of the most common reasons a VFD trips—and also two of the most commonly confused. While they both involve motor current, they point to very different problems and require different troubleshooting approaches. 
 
This guide explains the practical difference between overcurrent and overload faults, what usually causes each one in the field, and how to determine which direction to go before replacing parts. 

Why This Confusion Happens 

Both overcurrent and overload faults involve higher-than-normal current, but the way that current behaves over time is what matters. Drives react differently to fast current spikes than they do to sustained current draw. Understanding that distinction saves time and prevents misdiagnosis. 

What an Overcurrent Fault Really Means 

An overcurrent fault occurs when motor current rises too quickly or exceeds the drive’s instantaneous protection limits. The drive trips immediately to protect its output devices. 

• Common real-world causes: 

Shorted motor leads or damaged insulation 

Ground faults in the motor or cable 

Acceleration time set too short 

Motor wired incorrectly (delta vs wye) 

Severe mechanical binding or locked rotor 

Field clue: If the drive trips instantly on start or during rapid speed changes, you are likely dealing with an overcurrent condition. 

What an Overload Fault Really Means 

An overload fault is based on time. The drive monitors motor current and estimates motor heating using a thermal model. If current remains above rated levels for too long, the drive trips to protect the motor. 

• Common real-world causes: 

Worn or failing bearings 

Increased process load 

Misalignment or mechanical drag 

Undersized motor for the application 

Incorrect motor FLA programmed