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What is USF (under voltage fault) on an ATV630 process drive?

Published date: 18 February 2019

USF fault on an ATV630 process drive

Product Line:
Altivar 630, Process



The USF fault occurs when the DC bus voltage level drops below the threshold set in Compete settings, Error/Warning handling, Undervoltage handling.
In this submenu, you can change the value of what is considered undervoltage level, the timeout for the fault to appear, along with response to the fault.

- Measure the the incoming line to line voltages
- Compare the line voltage to the Mains Voltage as shown under Display menu, Drive parameters, and also the measurement of the DC bus voltage.
- If the standard line voltage is low, you can adjust the Mains voltage setting
- Adjust the Undervoltage time out to compensate for line contactors, or add time delay before a fault would occur. 

The DC bus of the drive can also be measured on terminals PA and PC.  This requires a true RMS cat 3 meter minimum.
Check for flat topping issues.  Check the load for high current draw.

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