Motor Starter Overload Trip

Motor starter thermal or electronic overload relay has tripped, cutting power to the motor to prevent winding damage from sustained overcurrent.

Probable Causes (ranked)

• Motor mechanically overloaded — jammed product, seized bearing, or obstruction on driven equipment
• Overload relay heater size incorrect for motor FLA — too small causes nuisance trips
• Single-phasing condition — one supply phase lost causing remaining phases to draw excess current
• Ambient temperature around starter enclosure too high — relay trips at lower current in hot panel
• Motor winding partially shorted — drawing above nameplate current under normal load

Fix Steps

1. 1 Let overload cool 5 minutes, then press reset button on the overload relay
2. 2 Measure motor current on all three phases with clamp meter — compare to nameplate FLA
3. 3 Check for single-phasing: measure voltage across all three phases at starter — should be balanced within 2%
4. 4 Verify overload heater or electronic overload setting matches motor nameplate FLA
5. 5 Check driven equipment for mechanical binding — try to rotate by hand with motor disconnected
6. 6 If ambient temperature is high, consider upsizing overload or improving panel ventilation
7. 7 Megger motor windings if overcurrent persists with no mechanical cause

Suggested Replacement Parts

Parts matched to fault category: Motor Overload Relay

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

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