There Was No Single Inventor
The electric motor is often credited to one person, but its history is a chain of contributions over roughly seven decades, made by people in several countries who frequently did not know of each other’s work. Priority questions are disputed in places, so this article describes what is reasonably well documented and notes where credit is shared or uncertain.
The Scientific Groundwork, 1800 to 1820
Before any motor could exist, there had to be a steady source of current. The voltaic pile, announced by Alessandro Volta around 1800, supplied it. In 1820 Hans Christian Oersted in Copenhagen observed that a wire carrying current deflected a nearby compass needle, showing a link between electricity and magnetism. Andre-Marie Ampere quickly worked out the mathematics of the forces between current-carrying wires.
These discoveries showed that a current could produce a force. Turning that force into continuous rotation was the next problem.
Faraday and the First Rotating Demonstrations
In 1821 Michael Faraday built a small apparatus in which a wire carrying current rotated around a magnet, dipping into a pool of mercury to complete the circuit. It converted electrical energy into continuous motion, but it was a demonstration, not a machine that could do useful work. A year later Peter Barlow described a spinning star-shaped wheel that worked on a related principle.
These devices are usually described as the first electric motors in the sense of a working principle. They produced very little power, and nobody could have run a workshop with them.
Electromagnets and the First Practical Machines
Real progress in the 1830s came from the electromagnet. William Sturgeon built an early electromagnet in the 1820s, and Joseph Henry in the United States greatly improved it with insulated wire wound in many turns. Motors began to use electromagnets in place of permanent magnets, which allowed stronger forces.
Several people built working rotating machines around this period:
- Anyos Jedlik, a Hungarian priest and physicist, built rotating electromagnetic devices in the late 1820s, which are often cited in Hungarian accounts of motor history.
- Moritz von Jacobi, working in Russia, built a motor in the 1830s and used a version in 1838 to power a small boat on the Neva River in St. Petersburg.
- Thomas Davenport, an American blacksmith, received a United States patent for an electric motor in 1837 and demonstrated machines that ran small models.
Each of these worked, but none competed with steam power. The reason was cost: the only available current source was the chemical battery, and zinc consumed in a battery was a far more expensive fuel than coal under a boiler.
The Generator Changes the Economics
The motor needed cheap electricity, and that arrived with the dynamo. Faraday had shown electromagnetic induction in 1831, and over the following decades inventors built generators driven by steam engines. In the mid-1860s several people, including Werner Siemens, Charles Wheatstone and Samuel Varley, described machines that used their own output to energize their magnets. Zenobe Gramme’s ring armature, from about 1871, produced smoother direct current and became widely used.
A key observation, which is often told in connection with an 1873 exhibition in Vienna, is that a generator can also run as a motor when supplied with current. Whether or not the story is told precisely, the principle was understood during the 1870s: the same type of machine could generate or use electricity. Once central power stations and electric lighting spread, motors had a supply to connect to.
Direct Current Motors Reach the Streets
Direct current motors were first used widely in transport. Frank Sprague designed motors that were successfully used on the streetcar system in Richmond, Virginia, which opened in 1888 and is often cited as a large early example of electric traction. Electric streetcars and subways spread rapidly in the following decade, and motors also entered elevators and printing machinery.
Alternating Current and the Induction Motor
Direct current motors depend on a commutator and brushes, which wear and spark. Alternating current offered a way around this. In the 1880s Galileo Ferraris in Italy and Nikola Tesla, who moved to the United States, independently described and demonstrated motors driven by a rotating magnetic field produced by multiphase currents. Tesla received patents in 1888. Around 1889 Mikhail Dolivo-Dobrovolsky developed a three-phase induction motor that was simple and robust, and three-phase systems became the standard form of industrial power in many countries.
The induction motor has no electrical connection to its rotor, needs little maintenance and starts without special devices, which is why it remains common today.
From Line Shafts to Factory Electrification
Early factories were driven by a single steam engine or water source turning long overhead shafts, with belts running to each machine. The whole line had to run even if only one machine was needed. As motors became reliable, factories gradually moved to group drive and then to a motor on each machine, a change that was most visible in the United States between about 1900 and the 1920s. Layouts no longer had to follow the shafts, lighting improved with the removal of belts, and machines could be started and stopped independently.
This was one of the factors behind assembly line production. The change did not happen overnight, since factories had sunk costs in existing steam plant, and adoption varied by industry and country.
Small Motors in the Home
Motors also became smaller and cheaper. Fractional-horsepower motors turned up in fans, sewing machines, vacuum cleaners and washing machines, and they were the basis of many electric kitchen appliances. The motor in a power tool such as a drill is a descendant of the same ideas, though modern designs use brushless electronics.
Later Development
Through the twentieth century, improvements in magnet materials, insulation, bearings and control electronics increased efficiency. Power electronics later made it practical to vary the speed of alternating current motors smoothly, which spread their use into transport, including electric vehicles, and into industrial robots. Electric motors now account for a large share of the electricity used in industry, though exact figures vary by country and source.
The arc of the story is a familiar one: a laboratory curiosity in 1821, a collection of small working machines in the 1830s, and a reliable industrial tool only after cheap generated electricity and alternating current systems arrived toward the end of the nineteenth century.