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Registered Member #1875
Joined: Sun Dec 21 2008, 06:36PM
Location:
Posts: 635
I am still working on gathering materials for my DRSSTC, and I have found that I have enough 30 AWG wire to construct a 6-inch diameter secondary about two feet high. I purchased a piece of acrylic tubing off ebay that fit those dimensions, but it is not perfectly circular... it is a bit squished, actually.
I happened to find some PVC the other day that happened to have 6" diameter, and it was of sufficient height, as well. Its walls were a bit thick, though.
So what am I better off using, the somewhat flattened acrylic, or the PVC? Or am I better off buying another piece of acrylic? I am *shooting for* optimum performance.
Registered Member #15
Joined: Thu Feb 02 2006, 01:11PM
Location:
Posts: 3068
Doesn't have to be perfectly circular. In fact, it could be square if you wanted it.
Just use the acrylic. You already have that.
Also, whether you use a cardboard, pvc, acrylic, or paper secondary, you really aren't going to see any difference in performance as the losses in the secondary are practically negligible compared to heating elsewhere, especially in your primary circuit.
Registered Member #15
Joined: Thu Feb 02 2006, 01:11PM
Location:
Posts: 3068
rp181 wrote ...
Round forms are used because there are not sharp corners, that it could corona on.
Yes, that is a good point, but it has been done several times before. I forget who it was, but they made a Tesla coil complete with a square primary, square secondary and even square (cube) toroid, and it worked pretty well.
Registered Member #540
Joined: Mon Feb 19 2007, 07:49PM
Location: MIT
Posts: 969
There wouldn't be too much corona on a square sec because the multiple windings would make the field strength not change that quickly. It would be as if the entire sec were one piece of metal (almost). What causes corona is when there is a field that changes quickly (like at the end of a needle). Is this right?
Registered Member #543
Joined: Tue Feb 20 2007, 04:26PM
Location: UK
Posts: 4992
Myke wrote ...
What causes corona is when there is a field that changes quickly (like at the end of a needle). Is this right?
Corona is the formation of plasma around a point of high potential gradient. The higher the curvature of the electrode - as in a needle point - the higher the potential gradient for the generation of plasma. Because of the large mass difference between electrons and positive ions, the behaviour of negative and positive coronas (i.e. where the needle point is positive or negative) are radically different. For example, the positive corona is rich in ultra-violet, while the negative corona is not.
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