How to Troubleshoot INVT Inverter Fault OL2 Motor Overload?

Getting the INVT inverter OL2 fault? This motor overload alarm means your motor is drawing too much current. Learn how to check your load, motor parameters, and inverter settings.

 

If your INVT inverter suddenly stops and displays OL2 on the keypad, it is signaling a Motor Overload fault. This means the motor connected to the inverter has been drawing current in excess of its rated value for a duration that exceeds the drive's thermal capacity.

The INVT drive uses an internal inverse-time thermal model to protect the motor. The OL2 fault is your drive’s way of saying: "The motor is running too hot, and if I don't stop now, the motor windings will be damaged."

Common Causes of OL2

• Mechanical Overload: The machine is physically jammed, the load is too heavy, or the bearings are seizing.
• Incorrect Motor Data: The motor’s rated current (found on the nameplate) is not correctly entered into the inverter’s parameters.
• Low-Speed Operation: The motor is running at a very low frequency for a long time, and its own shaft-mounted cooling fan is no longer spinning fast enough to dissipate heat.
• Voltage Imbalance: Input power issues causing the motor to draw unbalanced current.

Step-by-Step Troubleshooting Guide

1. Check the Mechanical Load

Before assuming it’s an electrical issue, check the mechanics:

• Turn the motor/load by hand while the power is OFF. Does it feel stiff?
• Check for seized bearings in the pump, fan, or gearbox.
• If the load is a conveyor, ensure it isn't carrying more weight than it was designed for.

2. Verify Parameter Settings

The INVT drive relies on accurate data to protect the motor. If these settings are wrong, the drive will "think" the motor is overloaded when it is actually running fine.

• Motor Rated Current: Check your drive parameters (usually in the P02 group). Ensure the Motor Rated Current parameter matches the value on the motor’s nameplate exactly.
• Thermal Protection Curve: Check the motor overload protection settings. If you are running a non-standard motor or one with a very high service factor, you may need to adjust the overload protection curve (if applicable).

3. Check for Cooling Issues

• Is the motor’s cooling fan obstructed by dust or debris?
• If you are running the motor at low speed (below 30Hz), the motor's internal cooling fan becomes ineffective. You may need to add an auxiliary forced-ventilation fan to the motor.

4. Check for Electrical Issues

• Use a clamp-on ammeter to measure the current on the U, V, and W phases while the motor is running. Compare these readings to the motor’s nameplate current.
• Ensure all electrical connections in the terminal box are tight. Loose wires cause high resistance, heating, and uneven current draw.

How to Reset the OL2 Fault

Once you have identified and fixed the mechanical jam or corrected the parameters:

1. Wait for the motor to cool down. An OL2 fault is based on a thermal model; trying to reset it while the motor is still physically hot will just result in the fault tripping again immediately.
2. Press the [RESET] button on the INVT keypad.
3. If the drive does not clear, perform a power cycle (turn the main supply off, wait for the screen to go blank, and turn it back on).

Summary Advice

If the OL2 fault happens frequently, do not simply increase the motor current parameter to make the fault go away. Doing so will bypass the protection designed to save your motor from a burnout. If the current is truly high, your motor is physically working harder than it should, and you must address the mechanical load or motor cooling to prevent a costly motor replacement.