How to identify and resolve OLF faults on ATV drives
This blog considers the cause of a motor overload fault (OLF) on Altivar drives. This applies to the following series: Altivar ATV12, ATV312, ATV32, ATV61, ATV71.
Motor overload fault (OLF) is triggered by the motor pulling current above the ItH (Motor Them Current) that is programmed into the drive. The further above the ItH setting the current is, the less time it will take to trip on OLF.
This fault detection codes that can be cleared with the automatic restart function, after the cause has disappeared. These faults can also be cleared by turning on and off or by means of a logic input (parameter Detected fault reset assignment rSF).
Note that by default the ATV drive does not store the thermal state of the motor when power is removed from the drive, so this fault could be reset by a power cycle without waiting for the motor to cool.
Check motor load.
Check motor nameplate settings in the drive. Also check current limitation settings. Verify the motor current is balanced in all three legs, and not exceeding the motor FLA. Check that the motor thermal current setting (ITH) is programmed according to motor name plate.
Schneider Electric’s recommendation is to change the motor thermal state memo from NO to YES. This means the OLF fault cannot be cleared by a power cycle. Instead power needs to remain on the drive until the calculated thermal state of the motor has dropped to an acceptable level.
The Motor thermal state is displayed in the Monitoring menu, parameter tHr. The drive will trip when the tHr parameter reaches 118%. It will not allow a reset until the tHr drops below 100%.
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