Alternator Brush Orientation

The ZM6 N is a negative brush control system, this means that the positive brush requires power at all times and the theory is we control the negative brush which controls the output of the alternator as per the setting on the ZM6,

The ZM6 P is a positive brush control system, this means that the positive brush is the field control and the negative brush is earthed.

American systems refer to A or B configurations as per below image