What Does a USF Fault Mean on an ATV312 Drive?

A USF (Undervoltage Fault) indicates that the input supply voltage to the drive has dropped below the minimum operating level required by the ATV31 or ATV312 drive.

When a USF fault occurs, the drive trips to protect itself from operating with insufficient voltage. This condition is typically caused by low incoming line voltage, voltage drops in the power supply, loose connections, or an undersized power source.

How to Troubleshoot a USF Fault

1. Use a digital multimeter to measure the input voltage at terminals L1, L2, and L3.
2. Verify that the measured voltage is above the minimum threshold for your drive model.
3. Inspect power wiring, fuses, circuit breakers, contactors, and supply connections for issues that could cause voltage loss.
4. Correct the supply voltage issue and reset the fault.

USF Fault Thresholds by Drive Rating

• ATV312 M2: USF fault occurs when line voltage is 160 VAC or lower
• ATV312 M3: USF fault occurs when line voltage is 160 VAC or lower
• ATV312 N4: USF fault occurs when line voltage is 300 VAC or lower
• ATV312 S6: USF fault occurs when line voltage is 430 VAC or lower

If this article does not answer your question, check out our FAQ database that has answers to more commonly asked questions:

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If this FAQ did not solve your issue, you can call us at 1-888-778-2733 Option 2 and then 4 or e-mail us atdrive.products.support@se.comto create a case with our Technical Support Team.

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