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How do I troubleshoot Supply Mains UnderVoltage faults on the Atlivar Process drives?

Drive is tripping on Supply Mains UnderV (USF) fault code.  

Product line:
Altivar Process, ATV630, ATV930, Altivar 600, Altivar 900


Supply voltage drops below trip level setting or transient drop in voltage.

Measure the line voltage with a meter.  Confirm the voltage reading matches on the Drive under the Main Menu > Display > Drive Parameters > Mains Voltage.  

Check the settings for Undervoltage.  Go to Complete Settings > Error/Warning Handling > Undervoltage handling.
Mains Voltage (URES) should match the measured and monitored line voltage.  For example, if using a 240V drive and the supply voltage is only 208V then change Mains Voltage to 200 VAC.  If using a 480V drive and your supply voltage is 450-470V, then change the Mains Voltage to 460V.  

UnderVolt Timeout (UST) - factory setting is 0.2 seconds.  Try increasing this to ride through a momentary voltage sag.
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