Alternators...Generators...What's the difference?

I thought I would take the occasion of a reader's question to expand on a topic that I am asked about quite frequently —  "what's the difference between an alternator and a generator?"

Question: I have a 1962 Chevy Nova with a straight 6 cylinder engine. I’m considering converting the original generator to an alternator. I would like to know the differences between a generator and an alternator, any pros and cons, and any difficulties in doing the conversion.

Answer: This is a very short question with a very long answer, so I’m going to have to keep it as simple as possible. Keep in mind that there is a lot more to alternators and generators than that which is contained here.

We’ll start with a simple explanation of how a generator functions, and then build on that to understand how an alternator works. A generator is basically an electric motor in reverse. An electric motor spins when electricity is applied, but a generator makes electricity when it is spun. The center of the generator is a series of windings called an armature, which spin inside of a series of fixed magnets thus producing an alternating (AC) current. Our cars are designed to run on direct (DC) current, so a commutator converts this electricity from AC to DC.

An alternator's construction is just the opposite of a generator. In an alternator the magnetic field is spun inside of a series of windings called a stator, thus producing electricity. Automotive alternators also produce AC and use a series of rectifiers to convert this AC to DC.

There are several advantages that alternators have over generators, and that’s why generators were virtually obsolete on cars by the mid 1960s. Alternators are simpler, smaller and lighter than generators. Unlike most generators, alternators produce enough current even at idle to charge a cars battery. An alternator is ready to work as soon as it’s installed. A generator must be “polarized” before it is used to insure the correct polarity.

I’ve converted many engines from a generator to an alternator, and it is not particularly difficult. The wiring is relatively simple and there is a lot of information on the internet including wiring diagrams. There are even aftermarket manufacturers that sell “jumper kits” to make the wiring easier. Finding the proper bracketry may be a little tricky. The lower alternator bracket from almost any GM product with a straight-6 cylinder engine that was equipped with an alternator should fit. The upper bracket will have to come from an alternator equipped GM car with the old style “pre-integrated” cylinder head.

Plan on spending a few hours to complete the conversion and you’ll be pleased with the results.

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About Steve Linden:

Steve was born in Brooklyn, New York in 1957. He grew up in a time and place where cars were worshipped, and none more so than the “American Muscle Car,” although this was a phrase that was'nt coined until decades later.By the age of twelve he was repairing just about anything with an engine.

Recognizing Steve’s early predilection for speed, his father strongly “suggested” a 1967 Lincoln Continental as Steve’s first car, believing that his son would be best protected in a “tank.” But the “need for speed” prevailed and the Lincoln was followed shortly by a 1970 Mustang, a 1964 LeMans and a memorable yellow 1970 Cuda.

Over one hundred cars have since followed.

Contact Steve today.