By 1960, automotive alternators were standard equipment for most car makes. Prior to that, generators had been used in vehicles because rectification of AC current into DC current required mechanical means until the advent of heavy-duty silicon diodes. Once diode rectifiers were available, the more expensive, heavier, higher-maintenance, lower-reliability generators were quickly replaced with alternators.
Electricity Generation in the 19th Century
Michael Faraday and Joseph Henry were first, in the 1920s, to document electromagnetic induction, which is the basic principle behind electrical power production. In 1832, a French inventor, Hippolyte Pixii, was the first to construct an electric dynamo. His early version was actually an alternator, but he did not know how to handle the alternating current, so he created a commutator to produce DC current. This first machine produced electricity only in pulses with each revolution.
It was not until 1860 that a continuous current DC generator was created by Antonio Pacinotti. Up to this point, only batteries were capable of providing useful levels of electrical current. Not until Zenobe Gramme used an iron core inside the magnetic field, in 1871, did the commercial generation of electricity become viable.
Seven years later, a Hungarian company began commercial installations of AC generators. At this point, the techniques for electricity generation were split between AC in Europe and DC in the U.S. market. Although it was clear that AC generators were more efficient, in America the problem was a lack of distribution infrastructure that could handle AC power. By the turning of the 20th Century, however, the largest generators built in America were AC generators, or alternators.
Automobile Electricity Production
Some early Model-T models had an AC generation system used solely for the engine ignition coil. Other cars usually had no electric generator at all because the starting battery, which only supplied spark, was the only piece of electrical equipment in the vehicle. It was charged infrequently by external means.
Only as cars became more sophisticated and employed electric starters, cigarette lighters, headlights, signals, radios and other electrical equipment, did the need for onboard power generation become necessary. DC generators at the time were the simplest to manufacture in spite of their operating deficiencies. Their major drawback is that the total current generated has to pass through the brushes and commutator, which require frequent replacement or refurbishment. Another serious disadvantage is that DC generators produce little or no power when the car’s engine is at idle speed.
World War II was the beginning of the end for DC generators in automobiles. U.S. military services demanded alternators on their vehicles because of their reliability and increased power to size ratio. Once an economical way to regulate an alternator’s three-phase AC output into DC was enabled by silicon rectifiers, the path was clear for their use in domestic cars as well.
Minor Drawbacks to Alternators
As car fuel efficiency has become a high priority in car design, automotive alternators have continued to evolve by becoming lighter and more power efficient. Early alternators required two horsepower of engine power to produce a single horsepower of electrical current. Modern alternators are up to 80% efficient at mid-range operating speeds.
DC generators do have a couple of advantages over alternators however. Reverse polarity or strong electrical spikes are far more likely to damage an alternator than a generator. Furthermore, in the case of a dead battery, a DC generator can still produce power, whereas an alternator may not or may damage itself due to high voltage.
We know our alternators. Contact us to find out which alternator can improve the performance of your industrial or commercial vehicle today.
Michael Faraday photo credit to Elliott Brown under cc 2.0
Model T photo credit to William Creswell under cc 2.0
The Tesla Model X photo credit to Steve Jurvetson under cc 2.0