What do the diodes do in a brushless AC altenator? Why are they useful and why are they needed? Charlie June 19, 2019 23:22 Follow In an brush-less AC alternator, the diodes rectify the AC current that is induced in the exciter rotor by the exciter stator to DC. This DC current is then fed through the main rotor to in turn induce a current in the main stator. Related articles What is an excitation system on an AC alternator? Why does it matter? How does it effect the voltage stability? What is an exciter stator? What does it do? How does it work? What is a PMG system on a generator? How does it work and why use one? What is a exciter rotor in an AC alternator? What does it do? How does it work? What are the main component parts of a diesel generator? Comments 0 comments Please sign in to leave a comment.