How to Troubleshoot ABB ACS850 Fault 65 IGBT Temperature?

Getting the ABB ACS850 Fault 65? This "IGBT Temperature" fault means your VFD is overheating. Learn how to check cooling fans, heatsinks, and ambient conditions to fix it.

 

The ABB ACS850 drive is designed to handle tough industrial environments, but its internal power electronics—the IGBTs (Insulated Gate Bipolar Transistors)—are highly sensitive to heat. If the drive trips with Fault 65 (IGBT Temperature), it has detected that the internal module temperature has exceeded a safe limit.

If the drive did not shut down, these power transistors would suffer permanent damage. Fault 65 is your drive’s way of saying it is starving for cooling. Here is your step-by-step plan to get the drive back to a normal operating temperature.

Common Causes of Fault 65

• Failed Cooling Fan: The internal fan responsible for pulling air through the heatsink has stalled or failed.
• Blocked Airflow: The drive's intake or exhaust vents are obstructed by debris, dust, or poorly designed cabinet ventilation.
• Dirty Heatsink: Dust and oil buildup on the cooling fins prevents effective heat transfer.
• High Ambient Temperature: The drive is installed in an environment that is too hot, or the cabinet lacks proper air conditioning/ventilation.
• Overload: The motor is drawing current near or above the drive’s maximum rating, generating more heat than the cooling system can dissipate.

Step-by-Step Troubleshooting Guide

Safety Warning: Always disconnect power and wait at least 5 minutes for the DC bus capacitors to discharge before opening the drive or inspecting the fans. Use a multimeter to verify zero voltage before proceeding.

1. Check Cooling Fan Operation

The cooling fan is a wear item and the most common cause of thermal trips.

• Power the drive up and listen. Can you hear the fan running?
• Check if the fan is rotating freely. If it is sluggish, making grinding noises, or completely seized, it must be replaced.
• Ensure the fan connector is securely plugged into the drive's control board.

2. Inspect Heatsink and Airflow

Even if the fan is spinning, it cannot cool the drive if the air path is blocked.

• Heatsink Fins: Inspect the aluminum heatsink fins. If they are clogged with "dust blankets" or oil/grease, use compressed air (at low pressure) to blow them out.
• Cabinet Environment: Is the drive mounted in a sealed cabinet? If so, verify that the cabinet's internal fans or air conditioning unit are operational.
• Clearance: Ensure there is enough space around the drive (top and bottom) for air to flow freely as specified in the ACS850 manual.

3. Analyze the Load (Motor Power)

If the drive and fan are perfectly clean, you might be pushing the drive beyond its thermal limits.

• Compare the motor’s nameplate power/current against the drive’s rated capacity. If you are consistently running at the drive's current limit, the IGBTs will inevitably run hot.
• Monitor current (Parameter 01.07) while the machine is running. If it is constantly nearing the drive's nominal output current, you may need a larger drive for this application.

4. Check Ambient Conditions

• Use a thermometer to check the temperature inside the electrical cabinet. If the cabinet temperature is consistently above 40°C–50°C, the drive's ability to cool itself is severely compromised.

How to Reset the Fault

1. Allow the drive and heatsink to cool down completely. A "hot" drive will trip Fault 65 again immediately if you try to restart it.
2. Once cool, press the [Reset] button on the ACS850 control panel.
3. If the fault keeps returning immediately upon starting, do not keep resetting the drive, as you risk destroying the power module. Check the cooling fan and heatsink cleanliness again.