F7802 fault in Siemens V70 Drive indicates the Infeed or power unit is not ready. This means the internal power components failed to signal a ready state after startup, often due to a missing DC link voltage or hardware failure.
Cause: After an internal power-on command, the infeed or drive does not signal ready because of one of the following reasons:
- Monitoring time is too short.
- DC link voltage is not present.
- Associated infeed or drive of the signaling component is defective.
Remedy:
- Ensure that there is a DC link voltage. Check the DC link busbar. Enable the infeed.
- Replace the associated infeed or drive of the signaling component.
