installation of a Tesla coil

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k33

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I work for a very large science museum. Our 'science show' division would like to install a large Tesla coil in a small theater we use for physics and chemistry shows. The theater measures 40' wide, 60 veet long, and perhaps 40' in height. The audience sits on aluminum bleachers on steep risers, about 20 feet from the stage.

A Tesla coil is a tuned rf transformer with a very high turns ratio. The primary coil is supplied by an oscillator, about 100kHz, and the secondary coil steps this up to voltages that range from 100kV to 1MV. The field intensity is very high at the secondary coil's terminal. This causes the air to break down in the vicinity and thus produces very large luminous streamers that radiate in all directions. The streamer current is very low, though it will cause local heating at the point of attachment. The high frequency assures that the capacitive impedance to earth from any metal object is quite low. Therefore, the arc will readily attach to most metallic objects in the vicinity.

Several of our maintenance people object to the installation of this device, citing possible damage to data cables and electronic equipment. My contention is that only light shielding--e.g., a large cube of chicken wire, will give complete protection to the data lines. There's also concern that the device may present a raspy load to the power line, thus causing havoc in attached equipment. It doesn't help that one of the old galleries is being converted to a radio/TV broadcast complex, though that equipment will be at the other end of our 1000-foot-long building. My only adverse encounter with our small Tesla coils is that sometimes they'll reset my digital watch to January 1, 12:01am.

If anyone has any experience with the bonding, grounding, power-line filtering, or other lore on Tesla coil installations we will be most grateful.

Mark Kinsler
COSI-Columbus, Ohio
 

don_resqcapt19

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Location
Illinois
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retired electrician
Re: installation of a Tesla coil

Mark,
I thought you guys already had a large Tesla coil or Vandergraph generator. I guess I must be wrong. I know that a number of science museums have this type of equipment and some use a Faraday cage (your chicken wire) to provide the shielding. Isn't there some type of network of science museums that you could go to for information on this subject?
PS, I just showed this question to my son and he says we should visit COSI again soon. We have been to both of them a number of years ago.
Don
 

hurk27

Senior Member
Re: installation of a Tesla coil

Mark The Faraday cage will work as at 100khz the wave length is much too long to escape it, But I would use a good low-pass filter in the driver stages and even at the output before the coil, as 4th and 5th harmonics would terrorize the AM broadcast band and might lead to a cease and decease order from FCC. Use a multi-point bonding connections to the chicken wire at equal places so the impedance of the wire don't get any RF holes or windows to leak RF out of, And don't forget the floor shielding as some do. As far as feed power yes it could ripple the input power @ 100khz but a good 60hz power line filter on the power supply should prevent it from getting into the rest of the museums power system.
 
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