Tesla coil

Tesla coil
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Name	Tesla coil
Inventor	Nikola Tesla
Introduced	1891
Type	Resonant transformer circuit
Related	Radio transmitter, Spark-gap transmitter, Alternating current, High-voltage engineering

Tesla coil is an electrical resonant transformer circuit invented by Nikola Tesla in 1891 to produce high-voltage, low-current, high-frequency alternating-current electricity. It was developed alongside Tesla's experiments with alternating current systems, wireless power transmission, and early wireless communication, influencing technologies such as the radio transmitter and the spark-gap transmitter. Tesla coils became iconic in demonstrations at institutions like the Columbia University and exhibitions including the World's Columbian Exposition.

History

Tesla developed the coil during an era of rapid innovation involving figures and institutions such as Thomas Edison, George Westinghouse, Westinghouse Electric Company, Bell Telephone Laboratories, and General Electric. Early demonstrations and patents were contemporaneous with experiments at Colorado Springs Laboratory and publicity events at venues like the American Institute of Electrical Engineers. Subsequent researchers and inventors including Guglielmo Marconi, Reginald Fessenden, Oliver Lodge, Heinrich Hertz, and organizations such as RCA and Harvard University examined resonant circuits and spark discharges. Academic work at places like Massachusetts Institute of Technology, Stanford University, University of Pennsylvania, and ETH Zurich expanded theoretical understanding, while patent disputes involved entities like Marconi Company and national standards bodies such as the International Electrotechnical Commission. Cultural diffusion placed Tesla coils into popular media produced by institutions like BBC and museums such as the Science Museum, London.

Design and principles

A Tesla coil typically comprises a primary circuit and a secondary circuit forming a resonant transformer, drawing on principles formalized by theorists including Michael Faraday, James Clerk Maxwell, Heinrich Hertz, Oliver Heaviside, and Lord Kelvin. The primary components — a primary capacitor, a primary coil, a secondary coil, and a spark gap or switching device — resonate at matching frequencies described in work by Jean-Baptiste Joseph Fourier and later modeled in texts from IEEE publications. Innovations in switching and control reference technology from firms like Siemens, Siemens AG, ABB, and semiconductor companies such as Intel and Texas Instruments for modern solid-state drivers. Resonance tuning, coupling coefficient, mutual inductance, and Q factor are analyzed in the context of frameworks advanced by Felix Savary and researchers at Bell Labs. High-voltage insulation and dielectric considerations involve standards influenced by bodies like Underwriters Laboratories and research from NIST.

Types and variations

Variants include the classic spark-gap coil used by Nikola Tesla and shown in early demonstrations, rotary spark gaps developed by companies like Westinghouse Electric, and triggered spark gaps used in military and research contexts at Los Alamos National Laboratory and Sandia National Laboratories. Solid-state Tesla coils (SSTCs) and double-resonant solid-state Tesla coils (DRSSTCs) employ power electronics from manufacturers such as Infineon Technologies and STMicroelectronics. Other variations include vacuum-tube oscillators inspired by Lee de Forest, pulse-forming networks used in particle accelerator facilities such as CERN, and magnetically coupled resonators applied in academic projects at MIT Media Lab and Caltech. Entertainment and art installations have used designs by groups like Cirque du Soleil and museums like the Exploratorium.

Operation and performance

Operation depends on energy transfer between the primary and secondary resonant circuits, a phenomenon elucidated by mathematical treatments from Joseph Henry to modern texts published by IEEE. Spark-gap types rely on ionization processes characterized in plasma physics studies at Princeton Plasma Physics Laboratory and diagnostic methods from Lawrence Livermore National Laboratory. Performance metrics include peak voltage, frequency, duty cycle, and radiated electromagnetic emissions; measurement and calibration reference standards from ANSI and ITU. Efficiency and scaling considerations have been explored in collaborations between universities such as University of Cambridge and industry partners like Siemens AG, with applied physics insights from researchers affiliated with Max Planck Society and Los Alamos National Laboratory.

Applications

Tesla coils have been used historically in experiments on wireless power transfer and early radio communication, influencing technologies developed by Marconi Company and research programs at Bell Labs. Contemporary uses include educational demonstrations at institutions like the Smithsonian Institution and the American Museum of Natural History, special effects in film and television productions by studios such as Warner Bros. and Universal Pictures, and musical "singing coil" performances employing modulation techniques developed by electronic musicians and studios like MIDI-enabled productions. Scientific applications encompass high-voltage testing at facilities like National Renewable Energy Laboratory and plasma research collaborations with Fermilab. Hobbyist and maker movements involving organizations such as Make: and events like Maker Faire continue to experiment with solid-state implementations.

Safety and legal considerations

Safety protocols draw on standards published by Occupational Safety and Health Administration and testing frameworks from Underwriters Laboratories. Risk assessments reference electromagnetic interference regulations enforced by Federal Communications Commission and international rules from International Telecommunication Union. Legal issues have arisen in relation to public demonstrations, venue liability policies overseen by entities like American Bar Association and insurance underwriters such as Lloyd's of London. Compliance with local electrical codes often involves coordination with municipal authorities and inspection bodies related to National Electrical Code administration.

Category:Electrical transformers Category:High-voltage engineering