Lynne Kiesling
Today’s Nikola Tesla’s 153rd birthday, as you can see celebrated in the Google page logo today (Hat tip: D.O.U.G., thanks!). If we owe our modern electricity-enabled civilization to any one scientist, it’s Tesla — alternating current, induction motors, transformers, you name it. Tesla rocks.
And for you 80s music fans, Tesla’s birthday post is yet again a thinly-veiled excuse to link to a great song from a great 80s band — “Tesla Girls”, Orchestral Manoeuvers in the Dark:
[youtube=http://www.youtube.com/watch?v=PVzEfR6wL70]
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Don’t forget about the hair band aptly called Tesla. They even put out a song called “Edison’s Medicine”.
But don’t we owe it in part also to direct current? While transmission is still done mostly in alternating current (though direct current is possible), most of our most amazing electric devices work not with alternating current but with direct current 😉
The issue isn’t so much about the usefulness of alternating versus direct current in various modern end uses as it is the practicality and economy of transmitting and distributing electricity efficiently to end users, especially considering the technologies available at the time. There was also a serious amount of resistance (no pun) to alternating current technology from the Edison camp, including many of the other prominent electrical engineers of the day.
That said, the crowning achievement of the entire Tesla multi-phase AC system, which included generators, transformers, and transmission, may have been the induction motor. Not only was the induction motor vastly superior to the DC machines of the day for industrial applications, but the AC system was able to deliver large amounts of energy to it without having to have a power plant right there at the load. The multi-phase *system* and the multi-phase induction motor were the ideas that originated mostly with Tesla. AC generators and transformers were known. It was just that nobody knew how to use them practically.
Going inside the machinery, Tesla’s contribution can be characterized as the rotating magnetic field, which he produced by arranging multi-phase coils around the inside of the cylindrical “stator,” the stationary part of the motor. In DC machines, the magnetic field is static, and you have to create alternating current in the rotor coils to get the thing to turn. This was accomplished with mechanical switching (using brushes and a commutator). In AC machines, the magnetic field rotates without switching and the rotor follows along without having to have any electrical connection to it, i.e., no brushes, no commutator. It is a much simpler machine, and much safer to use since it didn’t have a sparking commutator or brushes. It was the induction motor that provided the great end-use efficiency that transformed industry.