Motor Trips Overload Relay – Troubleshooting

Step-by-step diagnosis when overload relay trips. Mechanical vs electrical causes.

Symptom: Overload relay trips repeatedly

1. 1

   Check motor current

   Measure phase currents with clamp meter under load. Unbalanced phases (>10% deviation) indicate winding fault or supply issue.

2. 2

   Verify overload setting

   Overload must be set to motor nameplate full-load current (FLC). Incorrect setting causes nuisance trips.

3. 3

   Inspect mechanical load

   Binding bearings, blocked fan, jammed conveyor increase current. Check coupling and driven equipment.

4. 4

   Consider ambient temperature

   High ambient reduces overload trip time. Ensure adequate cooling and correct thermal class.