Dex Dexter wrote:
Just don't be discouraged! I will repeat VTTC twin system is the best option for your sculpture.VTTC generate less amount of ozone than SGTC. Sound level is reduced considerably. Twin systems does not need RF grounding! But really install grounded wire mesh in the glass house ;it acts like a Faraday cage suppressing EM interference.
Methinks you haven't actually done any analysis of Faraday cages around Tesla coils or measured the EM fields at least with respect to regulatory compliance.
As it happens, the cage will prevent a spark from going past the cage (which is the usual function),so you can pretty much prevent someone from getting a shock or hit by an arc, but it doesn't do a very good job suppressing EM interference.
Let's see.. you're operating at 100-300 kHz, so the wavelength is "very long" compared to the distances of interest. This means it's most likely a "near field" problem. Near field, from an EM situation, means you need to analyze both magnetic and electric fields, separately. The cage might do a find job controlling the electric field, but most cages are basically transparent to the magnetic fields, which, of course, hold just as much energy as the electric field.
Now let's talk about higher frequency interference (e.g. many MHz).. most of the cages I've seen for tesla coils are made of chicken wire or similar woven material. This isn't particularly good as a shield, because the strands go between the inside and outside of the cage. If you did it of welded mesh, then you're probably better off.
Now let's talk about "death to near by electronics" by induced transients from the sparks. Here, the propagation is mostly by the magnetic field in the circuit that goes topload, spark, ground, secondary coil... forming a loop with a perimeter of several meters. Unless you happen to have a shield that matches up with the magnetic field from the current in that loop, most of the transient field will happily couple to a nearby victim loop. This problem is most notorious with a Marx generator (really big di/dt, because the erected impedance is fairly low, unlike a TC, which has a big ol' honking inductor in the secondary circuit), but still an issue with a TC of any decent size.
Bottom line: a cage prevents shocks and direct arc contact, but not much for EMI, unless very carefully designed.
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