Cause : DC under voltage comes when the intermediate circuit voltage (DC link) drops below the under voltage limit. If the intermediate circuit voltage (UDC) is lower than the inverter's Undervoltage limit, the inverter will be switched off until the UDC once more goes above the undervoltage limit.

1. If the UDC remains under the undervoltage limit, the inverter will trip after a set time.
2. The time depends on the device and is set at 2-15 sec.
3. An undervoltage can occur when the connected AC line voltage is too low.
4. Check whether the supply voltage is suitable for the adjustable frequency drive.
5. When the adjustable frequency drive is switched off a warning 8 (and warning 6) is displayed briefly.
6. Note: Voltage warning low (warning 6) will thus also be able to generate an alarm 8.

• The time delay varies with unit size.
• Check that the supply voltage matches the frequency converter voltage.
• Perform an input voltage test.