Motor Thermal Overload Fault

What does OL1 mean?

The OL1 fault is triggered when the motor connected to the drive experiences prolonged overcurrent, causing it to exceed its thermal capacity. This protection is configured by parameters like L1-01 (protection selection) and L1-02 (overload time constant). Continuing to operate a motor in an OL1 condition severely risks damage to motor windings and insulation, leading to premature motor failure and costly downtime.

• Motor rated current (Parameter L1-01) set incorrectly in the drive, below the actual motor nameplate Full Load Amps (FLA).
• Mechanical overload on the motor shaft due to increased friction, binding, or a seized bearing in the driven equipment.
• Drive acceleration/deceleration times (Parameters C1-01, C1-02) set too short for the load inertia, leading to excessive peak current during transients.
• Supply voltage imbalance exceeding 2% at the drive input terminals (L1, L2, L3), causing higher current in one motor phase.
• Motor cooling fan failure or obstructed cooling fins on the motor itself, leading to insufficient heat dissipation.

Click steps to track your progress.

1. 1

   Read the motor nameplate and verify that Parameter L1-01 (Motor Rated Current) in the drive matches the motor's Full Load Amps (FLA). Adjust if necessary.

2. 2

   Measure the actual current (Amps) on all three motor phases using a clamp meter (e.g., Fluke 376 FC) during normal operation and compare to the value set in L1-01.

3. 3

   Disconnect power and manually rotate the motor shaft and connected load. Verify smooth, free rotation without excessive resistance or binding.

4. 4

   Using an insulation tester (e.g., Megger MIT420), perform a motor winding insulation resistance test from each phase to ground (500VDC for 1 minute).

5. 5

   Monitor motor temperature directly with a thermal imager (e.g., FLIR T540) and compare to the motor's insulation class limits (e.g., Class F, 155°C).

6. 6

   Verify supply voltage balance at the drive input terminals (L1, L2, L3) using a multimeter (e.g., Fluke 87V) and ensure phase voltages are within 2% of each other.