Nikola Tesla

1856-1943

The Serbian-American inventor whose rotating magnetic field gave the world the AC induction motor, a brushless, self-starting machine whose descendants spin in everything from pumps to electric cars.

Nikola Tesla was born in 1856 in Smiljan, then in the Austrian Empire and now in Croatia, the son of an Orthodox priest. He studied engineering and physics in the 1870s without finishing a degree, then got hands-on experience in telephony and at Continental Edison in Europe before emigrating to the United States in 1884. He worked briefly at the Edison Machine Works in New York, quit over a disputed bonus, and after a stretch of hardship (he dug ditches for two dollars a day) found backers and set up his own lab.

His central idea was the rotating magnetic field. Tesla realized that if you feed alternating currents that are out of phase with each other into a set of stationary coils, the combined magnetic field appears to rotate. Drop a conductor into that rotating field and it gets dragged along, turning without any electrical contact to the spinning part. The result, patented in 1888, was the AC induction motor: a simple, self-starting machine with no commutator and no brushes, which meant no sparking and far less maintenance than the DC motors of the day.

Tesla demonstrated his motor at the American Institute of Electrical Engineers in 1888, and Westinghouse Electric licensed his polyphase AC patents, making them the cornerstone of the AC power system. He went on to a flamboyant career of high-voltage, high-frequency experiments, wireless power dreams, and the unfinished Wardenclyffe Tower, spending most of his money along the way. He died in a New York hotel in 1943. In 1960 the SI unit of magnetic flux density was named the tesla in his honor.

The induction motor is still one of the great workhorses of electromechanical engineering, but Tesla's deeper legacy for modern hardware is the rotating-field principle itself. The brushless DC motors and permanent-magnet machines inside drones, robot joints, and electric vehicles all run on a controlled rotating magnetic field, now synthesized electronically by an inverter switching the phases in sequence. When firmware energizes a motor's coils in a precisely timed pattern to make the rotor chase a rotating field, it is automating exactly the effect Tesla discovered.

Fun facts

Tesla claimed he conceived the rotating magnetic field in 1882, years before he could build it. His 1888 induction motor turned that idea into a brushless, commutator-free machine, sidestepping the sparking and constant brush-replacement that plagued DC motors.
His big break came at the worst possible time financially. After being left penniless by investors who abandoned his first company, he was reduced to digging ditches before partners backed the lab where he developed the AC motor.
When Westinghouse hired Tesla to help power Pittsburgh's streetcars, his induction motor could only run at a constant speed, so it would not work for the start-stop demands of streetcars. They ended up using a DC traction motor instead, an early reminder that even a brilliant motor has to match the application.