Cause : Motor 1 field exciter low current comes when a low current condition in the field exciter circuit of Motor 1. The field exciter supplies DC current to the field winding of a DC motor, controlling its speed and torque.

F541 Motor 1 field exciter low current fault in ABB DCS800 drive indicates that the drive has detected a field current level below the required threshold for the motor’s proper operation. 

1. Check parameter settings of group 44 (field excitation: field current controller tuning, EMF controller tuning, flux linearization).
2. Check motor name plate for minimum current at maximum field weakening (maximum speed).
3. Check field circuit fuses.