What does Motor Overload / Overload Relay Trip mean?
Motor overload relay (thermal or electronic) detected current above rated FLA, shutting down motor.
Common causes
- Mechanical overload on motor shaft
- Single-phasing on 3-phase motor
- Low voltage causing high current draw
- Jammed impeller, fan, or driven load
- Incorrect overload relay setting
- Motor bearing failure increasing load
Diagnostic & testing steps
- 1. Allow motor to cool 10-15 minutes before resetting
- 2. Check overload relay trip current setting vs motor nameplate FLA
- 3. Measure running current on all phases with clamp meter
- 4. Compare to FLA: should not exceed 100% FLA continuously
- 5. On 3-phase: check for voltage imbalance >3% between phases
- 6. Check driven load for mechanical binding or jam
- 7. Test motor insulation with Megger: >1M ohm phase to ground acceptable
Tools required
- Clamp meter
- Multimeter
- Megohmmeter (Megger)
OEM parts & part numbers
Overload Relay, Motor Starter, Contactors
Part numbers: 3RU2116-1AB0, LRD10C
Safety warning
⚠️ LOCK OUT / TAG OUT: De-energize and lock out motor control panel before accessing motor or starter. Store energy (capacitors) may remain. Verify voltage is zero with meter before working.
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