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Alternator Presentation


For the most part, Alternators are relatively small and lightweight. The alternators found in most passenger cars and light trucks are constructed using an aluminum outer housing, as the lightweight metal does not magnetize.

This is important since aluminum dissipates the tremendous heat generated by producing the electrical power and since the rotor assembly produces a magnetic field.

If you closely inspect an alternator, you’ll find it has vents on both the front and back side. Again, this aids in heat dissipation.
A drive pulley is attached to the rotor shaft on the front of the alternator. When the engine is running, the crankshaft turns the drive belt, which in turn spins the pulley on the rotor shaft.

In essence, the alternator transfers the mechanical energy from the engine into electrical power.

Overrunning Alternator Pulley Units feature a robust, proven design based on sprag one-way clutch technology.

This unique design helps extend auxiliary drive belt service life for even the most severe customer specifications. Overrunning Alternator Pulley Units also help reduce belt load and optimize the front-end system.


  • The ability to deliver greater power in a more compact form is what the auto industry is looking for in terms of current alternator design
  • For the bearings within such products, the impact is evidenced in increases in rotational speeds, temperature and loads from the poly V belt now commonly used to supply power to systems such as the AC compressor, the pump for power steering, the water pump and the alternator.
  • Normally the alternator requires two deep groove ball bearings mounted on the rotor shaft. The bearings mounted on the drive end (pulley side) locate the rotor. Usually, these would be sizes 6303, 6302 or 6203. The bearings mounted on the other side (slip ring side) are axially free, i.e. non-locating, sizes 6203, 6202, 6003 or 6002.
  • Modern alternators have internal ventilation and are equipped with two high-performance fans located inside the alternator body at each end of the rotor coil. Previous designs have a single external fan behind the pulley. In some cases, to provide better servicing and other functions, the slip ring and its two brushes are located at the end of the rotor instead of between the two bearings.
  • The alternator generates direct current for recharging the battery and for powering vehicle electrical loads.