F4
UnderVoltage
Allen-Bradley · PowerFlex 4 Adjustable Frequency AC Drive
What does F4 mean?
An undervoltage fault indicates that the incoming AC line voltage has dropped below the drive's acceptable operating threshold. This can be caused by power sags or prolonged low line voltage conditions.
Source: Allen-Bradley PowerFlex 4 Adjustable Frequency AC Drive
Open Manual (Page 15)