Yes, it is possible supply the fan with an external supply, for this you need to change the terminal and supplied the R, S, T, terminal.
The terminals RO, SO & TO are for the supply of the main fans, It is only an AC supply. The purpose of this supply is to have a separate power supply for the fan if the drive is stopped/supplied by DC.
To use RO, SO & TO terminal you must reverse 2 connectors on the fan supply board (i.e. X4 to X1).Refer to attached file.

Released for: Schneider Electric India