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Registered Member #1879
Joined: Mon Dec 22 2008, 04:11AM
Location:
Posts: 40
Hi
I been playing around a little with a tesla coil that was originaly intended to become a 811AQ based VTTC but I never found any good cheap HV caps and I avoid paying premium for anything . The secondary I made ended up about 13 in of 27 AWG wire on a 4.5" tube when I ran out of wire..
When surfing around I found Steves Mini SST and I happened to have enough stuff in the junk box to get it running. It worked pretty good. I did not have a top load, only a piece of the wire and it ended up spinning around and throwing molten copper on the carpet. After browing it up twice I decided to build the Mini Brute power section since I like the idea of doubling the voltage and run the primary in resonance to. The prescribed 40N60 was to fancy so I got the $5 version. I can not se much advantage of using the big bricks, (Did I miss something here?) The design is built like a RF amplifier with hole mounted components mounted on the surface. I also use a junk box ferrite toroid for the gates. Seem to work but I don't really know how far I am from disaster.
Anyhow. I get about twice the spark length as before and it is quite ok but not impressive (no attempt to tune the primary yet). I measure the resonance to 330kHz on the seconday by wrapping a single turn around the base hooked to a sig generator and use a single turn pick up to the scope., If I add a topload made from two 11" stainless salad bowls I got from IKEA for a few bucks I end up at 240KHz. Is that a good frequency for the secondary?
Does it hurt to have stainless topload? The current should be minimal but there might be something I missed. Does it matter if the top cap is spherical?
What is a good guess for a primary coil design? I have 4 0.33uF caps in series. What is a good diameter and pitch for the coil? I was thinking of making it from 1/8 or perhaps 1/4 copper tubing. Currently I use 12 AWG cable. wrapped around a fiber glass sleave as shown but the primary is not tuned so I have no idea of what the operating frequency is
Registered Member #1733
Joined: Thu Oct 02 2008, 03:17PM
Location: Hamilton, ON, Canada
Posts: 100
I have 2 stainless steel Ikea bowls as a top load for my SGTC. I used AL tape to hold them together, drilled a small hole in the bottom one and fused 12AWG copper wire inside as a solder point for the secondary. Works great and only cost me $9. Looks just like your second pic...
No breakout on my coil, it just streams in every direction, but not once has it struck the secondary or primary coils...
A lot of people recommend buying gazing balls from a gardening store. They are polished stainless steel, but I can't find any locally...
Registered Member #989
Joined: Sat Sept 08 2007, 02:15AM
Location: São Paulo, Brazil
Posts: 476
240Khz? It might be ok, I run 244khz at my drsstc here, but not with that IGBT's, I used IRG4PC50UD and STGW30NC60W( or WD).
Some minibrick version can dissipate more heat than the TO-247 Version. But at HGTG40N60A4D I seen no difference at the datasheet heat dissipation (600W for both TO247 and SOT227)
Registered Member #1730
Joined: Thu Oct 02 2008, 08:12AM
Location: Poland
Posts: 35
I have stainless steel ball that I was prepering for TC, but it hve olny 8cm <->(3.5"), and my coil have 11cm(5") so, it will wait. I buy it in metalurgy shop (things for mechanic etc.) its 4€ or 5,5$.
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IKEA budget Mini Brute :-)
. The secondary I made ended up about 13 in of 27 AWG wire on a 4.5" tube when I ran out of wire.. 
nice!