How Nikola Tesla Invented the Modern AC Electric Motor
Nikola Tesla's 1888 patent for an induction motor that uses rotating magnetic fields to convert electricity into mechanical motion without needing physical brushes.
Original patent title: “Electrical Transmission Of Power”
Nikola Tesla's 1888 patent for an induction motor that uses rotating magnetic fields to convert electricity into mechanical motion without needing physical brushes. Granted to Individual in 1888 with 1 forward citation.
Coverage
What does this patent actually cover?
This patent describes an alternating current (AC) motor that eliminates the need for sliding electrical contacts, known as brushes, which were prone to sparking and wear in early direct current (DC) motors. It uses multiple sets of electromagnetic coils arranged in a circle, energized in a specific sequence to create a rotating magnetic field. This field induces an electric current in a central metal rotor, causing it to spin in synchronization with the magnetic field. This design allows for a robust, long-lasting motor that can run efficiently on the AC power grid.
The gap
What does this patent NOT cover?
- Does not cover direct current (DC) motors that rely on mechanical commutators and brushes.
- Does not cover single-phase AC motors that lack the specific multi-phase rotating field mechanism described.
- Does not cover power generation systems, only the specific motor configuration for converting electrical energy to rotational work.
These exclusions are unique to PatentBrief — derived from the actual claim language, not patent-office boilerplate.
Key facts
What made this novel
Tesla realized that by using polyphase AC, he could create a rotating magnetic field using stationary coils, removing the need for any physical connection to the spinning part of the motor.
The Patent Drawing
Schematic visualization of the patent's claim structure. Hand-drawn diagrams in progress for each landmark patent.
Where you've seen this
Real-world examples
Industrial conveyor belts
HVAC cooling fans
Electric vehicle traction motors
Household washing machine motors
Why it matters
The bigger picture
This patent is the foundation of the modern electrical grid and industrial automation. By proving that AC motors could be reliable and efficient, Tesla enabled the widespread adoption of alternating current, which could be transmitted over long distances, unlike the limited-range DC systems of the era.
Granted
May 1, 1888
Market context
Who's building on this
Companies in this space
Every major industrial motor manufacturer, including Siemens, ABB, and General Electric, continues to refine the principles of the induction motor. Modern EV manufacturers like Tesla, Inc. utilize advanced versions of these induction motors to drive their vehicles.
Market impact
This patent effectively ended the War of Currents, cementing AC as the global standard for power distribution. It enabled the electrification of factories and cities, creating the infrastructure that supports all modern industrial and consumer electronics.
Claim 1 — Plain English
What this patent covers
This patent describes an alternating current (AC) motor that eliminates the need for sliding electrical contacts, known as brushes, which were prone to sparking and wear in early direct current (DC) motors. It uses multiple sets of electromagnetic coils arranged in a circle, energized in a specific sequence to create a rotating magnetic field. This field induces an electric current in a central metal rotor, causing it to spin in synchronization with the magnetic field. This design allows for a robust, long-lasting motor that can run efficiently on the AC power grid.
The clever bit
Tesla realized that by using polyphase AC, he could create a rotating magnetic field using stationary coils, removing the need for any physical connection to the spinning part of the motor.
What it does not cover
- Does not cover direct current (DC) motors that rely on mechanical commutators and brushes.
- Does not cover single-phase AC motors that lack the specific multi-phase rotating field mechanism described.
- Does not cover power generation systems, only the specific motor configuration for converting electrical energy to rotational work.
Patent timeline
Application published, typically 18 months after filing
Patent officially issued
PatentBrief Score
Impact Score
Limited data
Citation count
6/40
Early citations
Claim breadth
0/20
Narrow claimsclaimsThe numbered statements at the end of a patent that legally define what the inventor owns.Read more →
Recency
0/20
Older than 20 years
Assignee scale
0/20
Independent or smaller assigneeassigneeThe entity that owns the patent — usually the inventor's employer or a company.Read more →
PatentBrief Impact Score — based on citation count, claim breadth, recency, and assignee scale. Not a legal assessment.
Heuristic Value Estimate
What this patent might be worth
$4K – $13K
Midpoint $8K · expired or expiring · industry ×1.4
Heuristic only — blends forward/backward citation counts, claim scope, time remaining, litigation history, and CPC-derived industry baseline. Real valuations need a professional appraisal.
Claim text not yet imported for this patent
Concepts involved
Citations
Patent lineage
Cite this patent
Tesla, N. (1888). How Nikola Tesla Invented the Modern AC Electric Motor (U.S. Patent No. 382,280). U.S. Patent and Trademark Office. https://patentbrief.org/patent/us/382280/tesla-ac-motor
Auto-generated from the patent record. Double-check author order and the issue date against the official USPTO document before submitting.
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Common Questions
Frequently Asked Questions
What does How Nikola Tesla Invented the Modern AC Electric Motor cover?
Nikola Tesla's 1888 patent for an induction motor that uses rotating magnetic fields to convert electricity into mechanical motion without needing physical brushes.
Who owns patent US 382280?
Individual owns this patent, granted in 1888.
When does this patent expire?
This patent has expired and is now in the public domain — anyone can use the invention freely.
What is patent US 382280 cited by?
This patent has been cited by 1 later patents that build on its ideas.
What problem does this patent solve?
This patent is the foundation of the modern electrical grid and industrial automation. By proving that AC motors could be reliable and efficient, Tesla enabled the widespread adoption of alternating current, which could be transmitted over long distances, unlike the limited-range DC systems of the era.
What does this patent NOT cover?
Does not cover direct current (DC) motors that rely on mechanical commutators and brushes.
Same assignee
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