How Do Alternators & Generators Work?

Your car's electrical system

The electrical system in your car is made up of several components. The battery, of course, gets most of the attention. However, it's in fact the alternator that does the majority of the work in your electrical system. When the system works as designed, you never notice it working, but when a key component such as the alternator starts to fail, it can eventuate into a major problem. An alternator is generally found at the front of your engine, connected via a serpentine belt. This belt runs directly from the engine's crankshaft to the alternator. The alternator translates the motion of the engine into usable energy and powers your electrical system, including your headlights, blower fan and radio.

The alternator

An alternator is generally made of a non-magnetic material such as aluminum and contains a number of parts, including a rotor, a stator and the output diodes. Each of these parts is necessary for the alternator to properly function. The rotor is the first step in the process. It is made of wire wrapped around a dense metal core, such as iron. When current is passed through the wire coil, it produces a low-level magnetic field. As the rotor spins, it allows the magnetic field produced in the wire coil to interact with the next component, the stator. The stator surrounds the rotor. The stator is made up of several windings. With each turn of the rotor, the magnetic poles interact with these windings which produces a small amount of current. This produces an alternating current which is unusable in modern automobiles and must be transformed in the output diodes. Since the diodes only permit electrical energy to flow in one direction, they can convert the unusable A/C power to D/C power which the battery can store.

The generator

Originally, automobiles were equipped with generators, instead of alternators. Generators work similarly to alternators. A generator produces current by passing a copper wire near a magnet which creates the current to supply electrical systems. These were originally attached directly to engines which provided the motion required. As the engine crankshaft rotated, it turned a copper wire near magnets. The magnet field interacts with the copper wire, producing electric current. This current was supplied directly to the battery. The battery supplied steady power to the car's electric lights, radio and air conditioner blower.