If you have ever been driving down the road at night and then had all of your electrical components begin to fail you have no doubt been a victim of an alternator going bad. It may start with your radio fading, then perhaps your dash lights, and before you know it your headlights are dimming as well. Then the unthinkable happens and your engine begins to spit and sputter and all of the sudden you are dead on the side of the road.
Often times people will mistake this kind of event for a battery going bad and in a way it true because the alternator and the battery are directly linked as the alternator is responsible for maintaining the battery’s power needs. So how exactly does an alternator work in getting power to a vehicle’s battery?
In the days before alternators a car’s electrical system was powered by generators. However, as the automobile became more sophisticated and required more power, the generators were no longer cutting the mustard and thus the alternator was born.
The alternator gets its name from the alternating current it produces as opposed to a direct current that is produced by a generator. But just as the scientist Tesla proved back in the year 1887 current that is alternating can generate voltage that is higher on a more efficient basis and this is something that is needed in the high tech vehicles of today.
Here is the rub; a car battery cannot use AC power. For that reason the alternator must first convert all the AC power to DC power so that it can then transfer that to the battery and the battery can use it for powering the electrical components of the vehicle. This is accomplished by the alternator feeding all of the AC power it generates into diodes that convert the AC to DC.
The two main components that generate power in the alternator are the rotor and the stator. As the engine runs it will rotate the alternator pulley and this causes the rotor to spin past three stator windings (wire coils) that surrounds an iron core that is fixed in place and makes up the stator. This is also known as a three-phase current.
The stator windings will be evenly spaced around the iron shaft at intervals of 120 degrees. The rotor produces an alternating magnetic field that creates an alternating current in the stator. This current will be an AC current which as stated earlier cannot be used by the vehicle’s battery. To address this issue, the AC current that has been generated is then sent through stator leads that go into a linking set of diodes. Both stator leads will have two diodes connected to regulate the flow of the current. The diodes then become a one way feed of DC power directly to the battery.
This converted AC/DC power will be used to power all of the vehicles electrical needs and ensure that the battery stays fresh and charged. So the next time your electrical system begins to act funny in your vehicle don’t be so quick to point the finger at your vehicle’s battery as it may just be your alternator giving you signals that it is on its last legs.
