Alternator Regeneration

Thread Starter


Joined Oct 1, 2008
In the section about automobile alternators on the main website a statement was made at the end of the article that quotes: "By rectifying the three-phase AC power produced, it is possible to have the alternator power its own field coil with DC voltage, eliminating the need for a battery. However, some independent source of DC voltage will still be necessary for start up, as the field coil must be energized before any AC power can be produced."

Question: Does this mean that the alternator will spin on its own power once it gets going and if so, how would the connections be made?


Joined Apr 20, 2004
No. The current through the armature produces a magnetic field. The magnatic lines of force passing across the field windings in the stator when the armature spins induce electric current. The DC source is necessary to produce the magnetic field in the beginning. As current is produced, the alternator feeds some back into the armature to keep the process going.

It takes as much power to spin the alternator as the power it produces, and then a bit, due to losses.