Induction motor

By 1888, the induction motor was waiting to be invented—twice. Alternating current technology had matured through the 1880s. The rotating magnetic field phenomenon had been demonstrated. The theoretical understanding of electromagnetic induction (Faraday, 1831) was well established. Two inventors on different continents, working independently with no knowledge of each other, assembled these components into essentially identical machines within months.

Galileo Ferraris, a professor at the Royal Industrial Museum of Turin, presented his paper on the rotating magnetic field and its application to motors in March 1888. He had conceived the idea in 1885 and built working models, but characteristically for an academic, he published for scientific priority rather than commercial protection. Ferraris explicitly declined to patent his invention, believing it should be freely available for scientific advancement.

Nikola Tesla, a Serbian immigrant working in New York, filed his patent applications in October and November 1887—before Ferraris's publication but after Ferraris's initial experiments. Tesla demonstrated his polyphase AC motor to the American Institute of Electrical Engineers in May 1888. Unlike Ferraris, Tesla was intensely interested in commercial application; George Westinghouse purchased his patents for $60,000 plus royalties, a fortune in 1888.

The convergent emergence was not coincidental but inevitable. The adjacent possible had accumulated the necessary components: understanding of alternating current, the transformer for voltage conversion, the theoretical framework for electromagnetic induction, and practical experience with DC motors that revealed their limitations. Both inventors were responding to the same technological pressures.

The induction motor's principle was elegantly simple. Instead of commutators and brushes (required for DC motors), alternating currents in multiple windings created a rotating magnetic field that induced currents in a rotor—hence 'induction' motor. The rotor followed the field, producing rotation without electrical connection. No brushes meant no sparking, no wear, and dramatically improved reliability.

The 'War of Currents' between Edison's DC and Westinghouse's AC systems made the induction motor's development urgent. AC could be transmitted over long distances (using transformers to raise voltage, reducing transmission losses), but practical AC motors had been lacking. The induction motor completed AC's technical superiority: generation, transmission, and utilization all worked better with alternating current.

Priority disputes were bitter but ultimately moot. Ferraris had demonstrated first but not patented; Tesla had patented first but demonstrated later. The Italian scientific establishment championed Ferraris; American business interests backed Tesla. Both had independently solved the same problem because the same problem existed in both places, and both had access to the same foundational knowledge.

The induction motor became the workhorse of industrial electrification. Its simplicity, reliability, and efficiency made it dominant in applications from factory machinery to household appliances. By 1900, AC systems with induction motors had won the War of Currents definitively. Today, induction motors consume approximately 45% of all electricity generated worldwide—a technology so successful it became invisible.