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A Layman's Guide To Alternators

Vehicle alternator being driven by fan belt

Alternators. By now, almost everyone has heard of, or at least been told how important the alternator is to keeping a car on the road. But what is it? And how can such a small part play such a big role in keeping a car on the road?

First off, let's talk about what the alternator does. Simply put, it's a little electrical generator that's responsible for supplying power to every electrical system in a car.

Why does the alternator matter?

Put simply, modern cars actually require a significant amount of electricity just to run, including some of the systems you probably wouldn't think of. Though you might think of the battery as the key part in the electrical system, the batteries main roll is really just to start the car and then the alternator does all the heavy lifting.

Realistically, cars just wouldn't be viable without the humble alternator.

So how does the alternator work?

Well, the alternator (usually) uses a belt-driven pulley to take mechanical energy from the engine and convert it into electrical energy.

The rotational energy from the engine is then transferred to the rotor (named because it rotates) spins inside a stator housing and creates an electromagnetic field. This field generates an alternating electrical current (AC current), which feeds the battery and the rest of the electrical system (AKA headlights, stereo and A/C fan).

"Hold on", I hear you saying, " Don't car batteries use DC current?"

Well yes. However, if you know so much about alternators why don't you write the blog post?


It is absolutely true that alternators (like all generators) inherently produce AC voltage which is why one of the key components of the alternator is the rectifier (or diode bridge in newer cars).

This simple bit of kit converts the AC current generated by the coils and magnets into DC current that can be used by the car's electrical system. The diode bridge is made up of a series of diodes, which act as one-way valves for the electrical current.

In addition to, the diode bridge normally tends to incorporate the voltage regulator which ensures that the electrical output is consistent and appropriate for the systems running in the car. This prevents the alternator from overcharging the battery or producing too much power, which could damage the electrical components of the car.

All in all, the alternator plays a critical role in the functioning of our cars. It generates the electrical power needed to run the car's electrical system, including charging the battery for the starter motor. So, the next time you turn the key just remember it's the alternator keeping you going - free of charge.


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