Motor Trips on Overload After a Few Minutes
Motor starts normally, runs for 3-5 minutes, then the overload relay trips and the motor stops.
Most commonly: undersized overload setting, single-phasing, mechanical overload on the driven load, or low voltage causing high current draw.
Lock out and tag out before opening any panel. Verify zero energy state. Use insulated tools and PPE rated for the panel's incident energy.
1) Measure running current on all three phases with a clamp meter and compare to nameplate FLA.
2) Check overload relay setting against actual FLA.
3) Check supply voltage at the motor terminals under load.
4) Check for mechanical binding on the coupled load.
Clamp meter, multimeter, megohmmeter, motor nameplate data
1. Confirm nameplate FLA and compare to the overload relay dial setting; correct if mismatched.
2. Run the motor and clamp each phase; an imbalance over 10% points to a supply or connection issue.
3. If current is balanced but high, inspect the driven equipment for mechanical drag, bearing wear, or blockage.
4. If voltage is low under load, trace the feeder for undersized cable or a loose connection.
Set up a quarterly thermal check on motor connections and verify overload settings whenever a motor is replaced or rewound.
Overload trips after a delay (not instantly) almost always point to a thermal/current issue rather than a wiring fault — start with current measurement before opening the motor.