no_PU fault in KEB COMBIVERT F5 Drive indicates the Power Unit is Not Ready. This means the control card is powered up but cannot communicate with the power stage, often because main power is missing or a cable is loose.
Cause:
The Power Unit Not Ready message may occur due to:
- Control card powered up by an external power supply, but the drive is not powered up by the line. Since the drive is not being powered by the line, the power stage cannot be identified.
- Connection issues between the control card and the power stage.
- Failure of the switching power supply.
Remedy:
- For inverter housing sizes G, H, R, U: Remove then reconnect the ribbon cable connecting the control card to the power stage at the control card connection.
- For inverter housing sizes D, E: Remove the control card then re-seat, ensuring correct pin connections.
- If reseating the ribbon cable does not resolve the issue, there may be a failure of the switching power supply. The drive will need to be replaced or inspected and repaired by KEB.
