Some embodiments relate to a controlled field alternator where the alternator is wired in a low wye configuration (coils wired in series or parallel). The first sensor measures the direct current flowing through the field within the alternator to detect an excitation level of a field within the alternator. As examples, the first sensor may measure field voltage, magnetic field intensity, magnetic flux density, current to the field of a rotating exciter, voltage to the field of a rotating exciter and the duty cycle of a pulse width modulated signal that controls an on-board rectifier for a permanent magnet exciter. Embodiments are also contemplated where the second sensor measures the RMS output voltage of the alternator to determine the output characteristic of the alternator.