# 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.

- **Patent:** US 382280
- **Original title:** Electrical Transmission Of Power
- **Owner:** Individual
- **Granted:** 1888
- **Status:** Active
- **Times cited:** 1
- **Field:** energy, mechanical, automotive

## What it does

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.

## 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.

## 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.

## Real-world examples

1. Industrial conveyor belts
2. HVAC cooling fans
3. Electric vehicle traction motors
4. Household washing machine motors

## Why it matters

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.

## 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.

**Full plain-English explainer:** https://patentbrief.org/patent/us/382280/tesla-ac-motor

**Original patent:** https://patents.google.com/patent/US382280

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_Source: PatentBrief — https://patentbrief.org. Patent facts are from public records; the plain-English explanation is PatentBrief's._


## Related patents

Semantically similar inventions in the PatentBrief corpus:

- [Nikola Tesla's Early System for Electric Lighting](https://patentbrief.org/patent/us/454622/tesla-coil-electric-lighting) — A 19th-century patent by Nikola Tesla describing an early method for distributing and regulating electric light using high-frequency alternating current.
- [How Marconi Patented Early Wireless Telegraphy Signals](https://patentbrief.org/patent/us/586193/radio-wireless-marconi) — Guglielmo Marconi's 1897 patent for sending electrical signals through the air to enable early wireless communication.
- [William Stanley Jr.'s Early Alternating Current Transformer System](https://patentbrief.org/patent/us/349611/transformer-stanley) — An 1886 patent describing an early design for an electrical transformer that helped make alternating current power distribution practical for homes and businesses.
- [How a Single Coil Powers Multiple Motor Armatures Simultaneously](https://patentbrief.org/patent/us/3723796/mri-cancer-tissue-detection) — A 1973 design for an electric motor that uses a single central coil to power several separate armatures arranged in a circle.
- [Nikola Tesla's Remote Control System for Boats](https://patentbrief.org/patent/us/613809/tesla-remote-control-teleautomaton) — Nikola Tesla's 1898 patent for controlling a boat's movement and steering from a distance using radio waves and electrical signals.