The generator has a single set of windings used to generate electricity. All of the electrical current made by the generator passes thru the two carbon brushes that ride on the commutator end of the armature.
Because there is only a single set of windings in a generator the output is limited at idle and low rpms, and the overall output is limited by the size of the field coils and the rest of the internal parts. Spinning the generator faster at higher rpms (above factory recommended rpms) will not increase output (will actually reduce output) because the brushes will begin to lift off of the commutator.
The other thing that happens is the generator overheats from excessive voltage, which causes the solder to melt that holds the segments onto the armature. When that happens the segments will come loose... bind up with the field coils and your generator is toast.
In the old days they called this..."throwing the solder out of the generator..." The same can happen when you adjust the regulator to increase output above the factory settings. The generator will overheat the solder will melt and you know the rest. You have caused more harm than good!
It also makes sense that the two biggest wear items on a generator are the brushes and the bearings on either end of the armature. When both are ignored either the brushes will wear down and become short enough that they no longer make good connection with the commutator or the bearing (in some applications bushings) wear out and the armature no longer runs true between the field coils. The armature can then rub on the field coils, damaging both the field coils and the armature. That means you would have to replace both the armature and the field coils...if you can find them!
Finally...new or rebuilt generators often suffer from improper installation. Mechanically, the installation is straightforward but electrically, things are a little more complicated. When the generator is removed from the vehicle for service there is residual magnetism stored in the pole field coils. The polarity of the generator is determined by the direction the current was traveling in the field coils when it was removed from the vehicle. If... during rebuilding and testing process the current is caused to flow in the opposite direction, (improper testing procedure) the pole shoes will change polarity.
If the generator is then installed on the vehicle, (and the generator not polarized) the reversed polarity will cause the electrical current from the generator to flow in the wrong direction, damaging the regulator (you would be sending positive ground current to your negative ground regulator) and discharging the battery when the car is left overnight. Therefore, all generators must be polarized after installation, and before running the car.
As we discussed earlier...generators produce direct current which is what all automotive electrical systems run on, even today. By contrast alternators produce alternating current and that current is converted to direct current. It has to do with efficiency... read on!
Alternators have the big advantage of producing a greater amount of current at low speeds as compared to a generator. In an alternator, the "field" windings are placed around the spinning central shaft rather than on "shoes" as in the generator. Two iron pole pieces, cast with "fingers" cover the field windings, and the fingers are interfaced. The fingers on one pole piece form the North poles and the fingers on the other form the South poles. This assembly is called the ROTOR.
Surrounding the rotor are a series of windings around laminated iron rings, attached to the alternator's case. This assembly is called the STATOR. The engine's crankshaft spins the rotor inside of the stator.
Direct current from the battery is fed through into the rotor's field coil by using brushes rubbing what are called slip-rings. One end of the field coil is fastened to the insulated brush, while the other end is attached to the grounded brush. As the pole fields pass through the stator, current is electromagnetically produced (just like in a generator) but since the rotor is composed of alternating North and South poles the current produced flows in opposite direction every 180-degrees of rotation. In other words, the current is "alternating."
Why is this more efficient? Because the stator windings are made up of three separate windings. This produces what is known as three-phase alternating current. When only one winding is used, single-phase current results (like in a generator). In effect, the alternator produces three times the current of a generator for the same effort on the engine's part. Also, alternators are considerably lighter and smaller than generators and can produce a greater amount of electrical current to cover increased electrical loads.
Converting Alternating Current To Direct Current
This is done by passing the alternating current thru silicon diodes. Diodes have the ability to allow current to flow readily in one direction only, stopping the flow if the direction reverses. Multiple diodes are arranged in alternators so that current will flow from the alternator to the battery (in one direction only, creating direct current) Diodes are a solid-state device which means they have no moving parts.
A Brief History Of Automotive Electrical Systems...
We have Allesandro Volta to thank for inventing the automotive storage battery in 1796. He had no idea at the time, that he was inventing what would become a significant part of the modern automotive electrical system. Volta made his discovery 89 years before the first car was offered for public sale. It would be another 25 years before the storage battery would even get a passing acknowledgement from the automakers.
Between 1885 and 1910, most cars and trucks that had gasoline engines did not need storage batteries because they had no accessories that required electricity. Ignition was powered by a magneto, which made its own current. In the rare event that additional electricity was needed, it was provided by a dry cell battery.
By 1911, storage batteries had attained a degree of reliability by being able to hold a charge for 30 days or longer. Once discharged, a storage battery could be recharged and put back into service, unlike dry cells, which were discarded. This degree of reliability was due in large measure to research and development done by the electric car industry, which needed reliable batteries so that their electric vehicles could compete with gasoline models.
The few gasoline car manufacturers who adapted the storage battery, began looking around to see what else they could do with the excess current the storage battery provided, and found electric lights.
The first electric lights were introduced on the 1898 Columbia. This was an electric car powered with storage batteries. Manufacturers of vehicles with gasoline engines typically used another way to produce light. It was the Prest-O-Lite lighting system, introduced in 1904. It was a steel cylinder containing pressurized acetylene gas that was fed to headlamps and ignited by flame.
With the adoption of storage batteries the automotive manufacturers then revived the dynamo, which had been around for some time. (Today we call the dynamo the generator, but in those early days most called magnetos were called "generators.") The battery then didn't have to be taken out of the car every month for recharging.
A problem encountered with the early dynamo-equipped electrical systems was battery overcharging. That problem was soon resolved with the development of a variable speed voltage regulator developed by Delco Company. This new voltage output regulator was first used on the 1912 Cadillac, which displayed another feature that took the auto industry by storm..." the self-starter."
The self-starter came about by accident -- literally. In the winter of 1910 on a wooden bridge on Belle Island Mich., a Cadillac driven by a woman stalled. Not having the strength to hand crank the engine herself, she was forced to wait on the bridge in the cold until help arrived.
In time, another motorist, also driving a Cadillac, happened along. His name was Byron T. Carter, and he was a close friend of the head of Cadillac, Henry M. Leland. Carter offered to start the woman's car, but she forgot to retard the spark and the engine backfired, and the crank flew off and struck Carter in the face, breaking his jaw.
Ironically, moments later another car carrying two Cadillac engineers, Ernest Sweet and William Foltz, came along. They started the woman's car and rushed Carter to a physician, but complications set in and a few weeks later Carter died.
Leland was devastated. He called a special conference of his engineers and told them that finding a way to get rid of the hand crank was top priority. “The Cadillac car will kill no more men if we can help it," he announced.
When the Cadillac engineers could not come up with a workable solution, Leland invited Charles F. Kettering and his engineers at Delco (still independent of GM) to work on a solution. Delco presented a working device in time for its introduction in the 1912 Cadillac models.
The Kettering Solution...
Kettering's device was a combination starting motor and generator, equipped with an overrunning clutch and reduction gear. Gear teeth engaged the flywheel to provide a reduction of about 25 to 1 between the starting motor and crankshaft, allowing sufficient torque to crank the engine successfully. General Motors brass didn't trust the new system at first, and demanded a backup magneto and hand crank.
As public confidence in the reliable battery/generator/self-starter system soared, it soon replaced the magneto in all General Motors cars. General Motors enjoyed a sales boom, and the remainder of the auto industry soon adopted the system. Of the 462 models shown at the 1911 New York Auto Show, only 19 had battery/generator systems, and they all had backup magnetos. Of 119 makes displayed at the 1924 New York Show, 110 had storage battery/generator systems and self-starters.
Other Electric Milestones...
In 1939, the first sealed-beam headlamps were introduced which made for much safer driving at night. That was followed in 1949, by the combination key operated ignition and starter switch which was introduced by Chrysler and eventually be adopted by all of the manufacturers.
Prior to 1949 on most vehicles, the starter was operated by a separate button on the dash or by a button on the floor above the accelerator pedal. Starting a car with the floor-mounted starter button was sometimes a challenge: your left foot was on the brake pedal, heel of your right foot on the accelerator, and the toe of your right foot pushing on the starter.
That was a lot going on at one time... especially if you were starting out on an incline. We truly have come a long way from those early days.
The Delco Company...
The Dayton Engineering Laboratories Co. (Delco) Company was founded in Dayton, Ohio, by Charles Kettering and Edward A. Deeds in 1909.
In 1918, General Motors (GM) acquired the United Motors Company which had been formed several years earlier by William C Durant to house several prominent parts manufacturers, including Delco, Dayton-Wright, and the Dayton Metal Products Company.
All of these latter companies were associated with Charles Kettering, Edward A. Deeds, and Harold E. Talbott. Kettering became vice president of General Motors Research Corporation in 1920. He held the position as head of research for GM for 27 years.
In 1936, Delco began producing the first dashboard-installed car radios. Based in Kokomo, Indiana, Delco Electronics employed more than 30,000 at its peak.
In early 1956, Delco developed a transistorized hybrid signal-seeking car radio, which used both vacuum tubes and transistors in its radio's circuitry. Transistors were used to replace the radio's audio output vacuum tubes and also the vibrator. This transistorized hybrid radio was available as an option on the 1956 Chevrolet Corvette car models.
In 1957, Delco produced an all-transistor signal-seeking car radio and was available for the 1957 Cadillac Eldorado Brougham car models. Delco became part of the General Motors Delphi Group in 1997.
Delphi Automotive traces as it's history back to the New Departure Bell Company, founded in Bristol, Connecticut, in 1888 to manufacture the earliest known doorbell-ringing device. The company's talent for innovation soon extended to transportation, with the 1897 introduction of the first bicycle coaster brake.
Other Delphi predecessors have been involved in automobile lighting since 1906 and manufacturing wooden auto bodies beginning in 1908.
In 1908, Albert Champion, who had been making spark plugs in America since 1899, joined Buick Motor Co. to make spark plugs in the AC Spark Plug Division, which was acquired by General Motors founder Billy Durant in 1909. Durant acquired Dayton Engineering Laboratories, which would become Delco, in 1914.
Other pre-Delphi innovations included the Ring Terminal, developed in 1930; the first car radio (1936); the first radio with mechanical push-button presets (1939); and mechanical power steering (1951).
As Paul Harvey used to say at noon everyday..."and now you know the rest of the story..."