Tesla Coil Topics

• high voltage capacitor
• gas discharge lamps
• tesla coils
• series resonant circuit
• spark gap
• lc circuit
• secondary coil
• tank circuit
• mercury vapor
• primary coil
• energy transfers
• street lighting
• voltage gain
• toroid
• primary energy
• convolutions
• capacitance
• output voltage
• square root

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Tesla Coil, Tesla Coil

Modified Tesla coils are widely used as igniters for high power gas discharge lamps, common examples being the mercury vapor and sodium types used for street lighting. Although electronic igniters are available, Tesla's original spark gap design is much cheaper and has proven extremely reliable.

This Tesla coil had the secondary being inside of, and surrounded by, the convolutions of the primary coil. This Tesla coil consisted of a primary and secondary wound in the form of a flat spiral. One coil, the secondary in step-up transformation, of the device consisted of a longer fine-wire. The apparatus was also connected to ground when the coil was in use.

However, the voltage gain of a disruptive Tesla coil can be significantly greater, since it is instead proportional to the square root of the ratio of secondary and primary inductances. The coil transfers energy from one oscillating resonant circuit (the primary) to the other (the secondary) over a number of RF cycles. As the primary energy transfers to the secondary, the secondary's output voltage increases until all of the available primary energy has been transferred to the secondary (less losses). Even with significant spark gap losses, a well designed Tesla coil can transfer over 85% of the energy initially stored in the primary capacitor to the secondary circuit.

These typically consist of a primary tank circuit, which is a series LC (inductance-capacitance) circuit composed of a high voltage capacitor, spark gap, and primary coil; and the secondary LC circuit, a series resonant circuit consisting of the secondary coil and the toroid. In Tesla's original plans, the secondary LC circuit is composed of a loaded secondary coil which is then placed in series with a large helical coil. The helical coil was then connected to the toroid. Most modern coils use only a single secondary coil. The toroid actually forms one terminal of a capacitor, the other terminal being the Earth (or "ground"). The primary LC circuit is "tuned" so that it will resonate at the same frequency as the secondary LC circuit. The primary and secondary coils are magnetically coupled, creating a dual-tuned resonant air-core transformer. However, unlike a conventional transformer, which may couple 97%+ of the magnetic fields between windings, a Tesla coil's windings are "loosely" coupled, with the primary and secondary typically sharing only 1020% of their respective magnetic fields. Earlier oil insulated Tesla coils needed large and long insulations at their connections to prevent discharge in air. Later version Tesla coils spread their electric fields over large distances to prevent high electrical stresses in the first place, thereby allowing operation in free air.

The resonant primary circuit is formed by connecting a capacitor in series with the primary winding of the coil, so that the combination forms a series tank circuit with a resonant frequency near that of the secondary circuit. Because of the additional resonant circuit, one manual and one adaptive tuning adjustment are necessary. Also, an interrupter is usually used to reduce the duty cycle of the switching bridge, in order to improve peak power capabilities; similarly, IGBTs are more popular in this application than bipolar transistors or MOSFETs, due to their superior power handling characteristics. Performance of a DRSSTC can be comparable to a medium power spark gap Tesla coil, and efficiency (as measured by spark length versus input power) can be significantly greater than a spark gap Tesla coil operating at the same input power.

This can induce corona discharges between turns that weaken and eventually destroy the transformer's insulation. Experienced Tesla coil builders almost exclusively use the top circuit, often augmenting it with low pass filters (resistor and capacitor (RC) networks) between the supply transformer and spark gap to help protect the supply transformer. This is especially important when using transformers with fragile high voltage windings, such as Neon-sign transformers (NSTs). Regardless of which configuration is used, the HV transformer must be of a type that self-limits its secondary current by means of internal leakage inductance. A normal (low leakage inductance) high voltage transformer must use an external limiter (sometimes called a ballast) to limit current. NSTs are designed to have high leakage inductance to limit their short circuit current to a safe level.

Tuning can then be adjusted so as to achieve the longest streamers at a given power level, corresponding to a frequency match between the primary and secondary coil. Capacitive 'loading' by the streamers tends to lower the resonant frequency of a Tesla coil operating under full power. For a variety of technical reasons, toroids provide one of the most effective shapes for the top terminals of Tesla coils.

Tesla coil discharges are formed as a result of displacement currents as pulses of electrical charge are rapidly transferred between the high voltage toroid and nearby regions within the air (called space charge regions). Although the space charge regions around the toroid are invisible, they play a profound role in the appearance and location of Tesla coil discharges.

The unique combination of a rising high voltage Radio Frequency envelope and repetitive pulsing seem to be ideally suited to creating long, branching discharges that are considerably longer than would be otherwise expected by output voltage considerations alone. High voltage discharges create filamentary multi-branched discharges which are purplish blue in colour. High energy discharges create thicker discharges with fewer branches, are pale and luminous, almost white, and are much longer than low energy discharges, because of increased ionisation. There will be a strong smell of ozone and nitrogen oxides in the area. The important factors for maximum discharge length appear to be voltage, energy, and still air of low to moderate humidity. However, even more than 100 years later after the first use of Tesla coils, there are many aspects of Tesla coil discharges and the energy transfer process that are still not completely understood.

Tesla made a proposal that there needed to be "thirty" such antennas worldwide. Marc J. Seifer, Wizard: The Life and Times of Nikola Tesla . Page 472. ( cf . "Each tower could act as a sender or a receiver. In a letter to Katherine Johnson, Tesla explains the need for well over thirty such towers".) The receiving circuit of these towers are connected each with a condenser and a device adapted to open and close the receiving circuit at predetermined intervals of time. U.S. Patent 0685956 The Tesla coil receiver has means for commutating, directing, or selecting the current impulses in the charging circuit so as to render them suitable for charging the storage device, a device for closing the receiving-circuit, and means for causing the receiver to be operated by the energy accumulated.

Impedance, generally though, is not applied in an obvious way; for electrical impedance, the impedance at the load ( e.g ., where the power is consumed) is most critical and, for a Tesla coil receiver, this is at the point of utilization (such as at an induction motor) rather than at the receiving node. Complex impedance of an antenna is related to the electrical length of the antenna at the wavelength in use. Commonly, impedance is adjusted at the load with a tuner or a matching networks composed of inductors and capacitors.

US685957 Utilization of Radiant Energy The helical resonator can be "shock excited" due to radiant energy disturbances not only at the fundamental wave at one-quarter wave-length but also is excited at its harmonics. Hertzian methods can be used to excite the Tesla Antenna with limitations that result in great disadvantages for utilization, though. U.S. Patent 0685953 Apparatus for Utilizing Effects Transmitted from a Distance to a Receiving Device through Natural Media The methods of ground conduction and the various induction methods can also be used to excite the Tesla Antenna, but are again at a disadvantages for utilization. U.S. Patent 0685953 Apparatus for Utilizing Effects Transmitted from a Distance to a Receiving Device through Natural Media The charging-circuit can be adapted to be energized by the action of various other disturbances and effects at a distance. Arbitrary and intermittent oscillations that are propagated via conduction to the receiving resonator will charge the receiver's capacitor and utilize the potential energy to greater effect. U.S. Patent 0685953 Apparatus for Utilizing Effects Transmitted from a Distance to a Receiving Device through Natural Media Various radiations can be used to charge and discharge conductors, with the radiations considered electromagnetic vibrations of various wavelengths and ionizing potential. US685957 Utilization of Radiant Energy The Tesla Antenna utilizes the effects or disturbances to charge a storage device with energy from an external source (natural or man-made) and controls the charging of said device by the actions of the effects or disturbances (during succeeding intervals of time determined by means of such effects and disturbances corresponding in succession and duration of the effects and disturbances). U.S. Patent 0685954 Method of Utilizing Effects Transmitted through Natural Media The stored energy can also be used to operate the receiving device. The accumulated energy can, for example, operate a transformer by discharging through a primary circuit at predetermined times which, from the secondary currents, operate the receiving device. U.S. Patent 0685954 Method of Utilizing Effects Transmitted through Natural Media While Tesla coils can be used for these purposes, much of the public and media attention is toward the transmitting applications of the Tesla coil since the plasma discharges are fascinating to most people. Regardless of this fact, Tesla did suggest that this variation of the Tesla coil could utilize the phantom loop effect to form a circuit to induct energy from the Earth's magnetic field and other radiant energy sources (including, but not limited to, electrostatics "Both kinds of strains exist in radiant energy, [2] The stresses in electro-magnetic energy are at right angles both to the electrostatic stresses and to the direction of their motion or flow." ). With regard to Tesla's statements on the harnessing of natural phenomena to obtain electric power, he stated: Ere many generations pass, our machinery will be driven by a power obtainable at any point of the universe. "Experiments with Alternate Currents of High Potential and High Frequency" (February 1892) Tesla stated that the output power from these devices, attained from Hertzian methods of charging, was low, U.S. Patent 0685953 "Apparatus for Utilizing Effects Transmitted from a Distance to a Receiving Device through Natural Media" but alternative charging means are available. Tesla receivers operated correctly, act as a step-down transformer with high current output. A. H. Taylor, " Resonance in Arial Systems ". American Physical Society. Physical review. New York, N.Y.: Published for the American Physical Society by the American Institute of Physics. ( cf.

The power levels achieved by Tesla coil receivers have, thus far, been a fraction of the output power of the transmitters.

On the load side, 700 MW is seen to correspond to two million parsimonious households averaging 350 watts of power use, contrasted with a world population of over six billion people. As regards methods, atmospheric electricity includes static electricity and other phenomena. Modern HVDC technology inverts DC at such voltages to AC well enough to be very popular for use in the power grid; a Tesla coil variant is not the only way to do this, nor necessarily the best way, either for atmospheric electricity or telluric power.

A Tesla coil is not a wideband device insofar as it operates only on its resonant frequency and certain harmonics.

Since the body no longer provides a warning 'shock', novices may touch the output streamers of small Tesla coils without feeling painful shocks. However, there is anecdotal evidence among Tesla coil experimenters that temporary tissue damage may still occur and be observed as muscle pain, joint pain, or tingling for hours or even days afterwards.

Even lower power vacuum tube or solid state Tesla coils can deliver RF currents that are capable of causing temporary internal tissue, nerve, or joint damage through Joule heating. In addition, an RF arc can carbonize flesh, causing a painful and dangerous bone-deep RF burn that may take months to heal. Because of these risks, knowledgeable experimenters avoid contact with streamers from all but the smallest systems. Professionals usually use other means of protection such as a Faraday cage or a chain mail suit to prevent dangerous currents from entering their body.

Should a high frequency arc strike the exposed primary coil while, at the same time, another arc has also been allowed to strike to a person, the ionized gas of the two arcs form a circuit that may conduct lethal, low-frequency current from the primary into the person. This is believed to have been the cause of death of a professional Tesla coil demonstrator, Henry Leroy Transtrom, in 1951.

A Magnifier uses a 2-coil 'driver' to excite the base of a third coil ('resonator') that is located some distance from the driver. The operating principles of both systems are similar. The world's largest currently existing 2-coil Tesla coil is a 130,000 watt unit, part of a 38 foot tall sculpture. It is owned by Alan Gibbs and currently resides in a private sculpture park at Kakanui Point near Auckland, New Zealand.

They do use inductive "kick", the forced, abrupt decay of the magnetic field, such that a voltage is provided by the coil at its primary terminals that is much greater than the voltage that was applied to establish the magnetic field, and it is this higher voltage that is then multiplied by the transformer turns ratio. Thus, they do store energy, and a Tesla resonator stores energy. A modern, low power variant of the Tesla coil is also used to power plasma globe sculptures and similar devices.

The world's largest conical Tesla coil is on display at the Mid America Science Museum in Hot Springs, Arkansas. This coil produces 1.5 million volts of electrical potential. A very large tesla coil, designed and built by Syd Klinge, is shown every year at the Coachella Valley music and arts festival, in Coachella, Indio, California, USA. There are "coiling" conventions where people attend with their home-made Tesla coils and other electrical devices of interest.

Interview with ArcAttack on Odd Instruments Duckon 2007-Steve Ward's Singing Tesla Coil video The YouTube video Super Mario Brothers theme in stereo and harmony on two coils shows a performance on matching solid state coils operating at 41 kHz.

Also in the Fallout series of games fictional Tesla Armor can be found. Tesla armor provides great protection from energy weapons because, in the game's context, the armor absorbs and dissipates most of the attack much like a Tesla coil does when discharging.

Source: Wikipedia > Tesla Coil