The Internal Serial Link Fault (INF3) occurs in Altivar 61/71 Drives when the 24VDC internal power supply is disturbed, causing the reset of microprocessor. The second likely reason is that the communication between the internal boards i.e. Power board, Motor Control board and Application Board is disrupted.
To remove the fault, check the internal connections, tightness of ribbon cable & connectors of internal boards. Also ensure that the power cable and the control cable are separated in the external wiring. Lastly replace the Motor Control Board or the Terminal Board.