Now that the mechanical construction of the alternator rotor and stator has been reviewed, understanding how these two alternator components working together to produce electrical energy will be discussed.

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Without going into a lengthy dissertation about electricity, magnetism, and electromagnetic induction, a simple explanation will be given. When a magnetic field is passed over a conductor, i.e., copper wire, or when a conductor is passed through a magnetic field an electrical charge is produced in the wire. Passing a magnetic field over a stationary wire is converting mechanical energy to electrical energy. Passing a wire through a stationary magnetic field converts electrical energy to mechanical energy. An alternator or generator changes mechanical energy to electrical energy, i.e., a moveable electromagnet passes over a stationary wire. In the case of the alternator the rotor is the electromagnet which induces electrical energy into the alternator stator. Since the rotor has north and south magnetic poles, the electrical charge produced in the stator is positive and negative or alternating energy or current. In order for this current to be used in the vehicle it has to be converted to direct current which is the job of another component in the alternator.

The power of the alternator depends upon a number of items, size and amount of windings in the stator, the size of the rotor magnetic poles, the amount of windings in the rotor, how fast the rotor is spinning, and the amount of electrical energy flowing through the rotor. The last two items are the easiest to change. The rotor speed is determined by the size of the alternator pulley and engine speed. The electrical energy flowing through the rotor is controlled by the amount of electrical energy or voltage being applied to the rotor, the more voltage the stronger the magnetic field, the stronger the electrical output.

For a quick review, the alternator is a device that converts mechanical energy into electrical energy. The alternator rotor is an electro-magnet which spins inside a stationary set of wires wrapped around an iron core called a stator. The electro-magnetic strength is determined by the number of windings and size of the north and south poles on the rotor, rotor speed, and the amount of electrical energy flowing through the rotor. The rotor induces an alternating current, because of the north and south poles on the rotor, into the stator. This alternating current is converted to direct current by another component is the alternator.

As always, if any procedure in this series of articles appears to be beyond the capabilities of the vehicle owner or driver, then testing and servicing the alternator should be performed by a professional or ASE Master Certified mechanic. The vehicle would have to be taken to a repair shop that employs these types of mechanics such as A & M Alternator Services located at 2419 E. Jackson St. in Phoenix, Auto Electric Specialists located at 5216 W. Lamar Rd. in Glendale, Village Auto Electric Service located at 19 N. Miller St. in Mesa, All Start Electric located at 13501 E. Chandler Blvd. in Chandler, Jordan’s Automotive Specialists located at 8718 E. McDowell Rd. #3 in Scottsdale, or Rob’s Quality Automotive located at 11801 N. Cave Creek Rd. in Phoenix

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