History
- 1820s — Coils and electromagnets. Work by Oersted, Ampère, Sturgeon, and Joseph Henry established the relationship between current, coils, and magnetic fields.
- 1831 — Faraday's induction experiments. Michael Faraday demonstrated that changing magnetic flux induces voltage in another circuit. His iron ring with separate windings is a direct transformer ancestor.
- 1830s–1850s — Induction coils. Interrupter-driven coils produced high-voltage pulses for experiments, ignition, and medical apparatus.
- 1870s–1880s — AC lighting. Alternating-current systems created the practical need to transfer energy between voltage levels.
- 1885 — ZBD system. Zipernowsky, Bláthy, and Déri developed practical closed-core, parallel-connected transformers for AC distribution at Ganz.
- 1880s — Stanley and Westinghouse. William Stanley developed practical transformer and distribution systems for George Westinghouse in the United States.
- 1890s — AC distribution expands. Transformers made high-voltage transmission and low-voltage local use practical.
- Early 20th century — Radio and telephone. Transformers coupled tube stages, matched speakers, isolated lines, and powered equipment.
- Mid-20th century — Ferrites. Ferrite cores enabled much higher-frequency transformers with lower eddy-current loss.
- Late 20th century — Switch-mode power. Semiconductor switching moved many transformers from 50/60 Hz into tens or hundreds of kilohertz, greatly reducing size.
- Today. Transformers range from tiny RF structures to utility units weighing hundreds of tons.
Why it mattered
Transformers solved one of electrical power's central problems: efficient long-distance transmission at high voltage while still supplying safe and useful local voltages.
Electronics too
Tube equipment used power transformers, interstage transformers, chokes, and output transformers. Later solid-state equipment kept transformers where isolation, conversion, impedance matching, or magnetic energy transfer remained useful.