HOSE AS 3221687 - Caterpillar

Permanent Magnet Excited Generators
Permanent magnet pilot excited (PMPE) generators receive power for the voltage regulator from a pilot exciter, rather than the main armature as in self-excited generators. The pilot exciter consists of permanent magnet (PM) and PM armature. The pilot exciter operates independently from the generator output voltage. Constant excitation during large load application is possible, because the irregularities that occur in generator output voltage (caused by load conditions) are not fed back into the exciter. The independent operation also allows the generator to better sustain an overload for a short duration.Self-Excited Generators
Self-Excited generators receive power for excitation and voltage sensing for the regulator from the main armature (stator) output of the generator. The voltage regulator senses the generator output voltage and provides regulated output to the generator exciter. The exciter then provides power to the main rotating field (rotor). As the main field rotates, a voltage is induced into the main armature (stator) to causes a generator output.