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steel vs copper or brass in tesla coil

Thread starter #1
ive heard from a couple of my viewers that i should not use steel as a conductor on my tesla coil, that i should use copper or brass instead. i would like some input on this from more experienced people. please elaborate! i am using steel strapping for my cap bank as well as steel 'L' brackets and screws in my spark gap. im also using steel screws in my richard quick spark gap. any input is welcome!!

http://www.youtube.com/watch?v=hh3vilo6OL4&feature=plcp

http://www.youtube.com/watch?v=mVsZIFiDD0o&feature=plcp
 
#2
if the caps get warm but the steel doesn't then you're probably fine. but if the steel gets warm before the capacitors do then you should see an improvement by switching to copper, brass, aluminum or practically anything nonmagnetic.

the issue with steel isn't the conductivity (which isn't that un acceptable if you just use a lot of it.) but the permeability which further reduces the skin depth.

another thing you might consider doing is cutting the primary in half and configuring the capacitors for double the capacitance/half the voltage.

i don't know what the numbers are for your tesla coil but you may not have enough KVA in the primary tank.
 
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DerStrom8

Super Moderator
Most Helpful Member
#3
ive heard from a couple of my viewers that i should not use steel as a conductor on my tesla coil, that i should use copper or brass instead. i would like some input on this from more experienced people. please elaborate! i am using steel strapping for my cap bank as well as steel 'L' brackets and screws in my spark gap. im also using steel screws in my richard quick spark gap. any input is welcome!!

http://www.youtube.com/watch?v=hh3vilo6OL4&feature=plcp

http://www.youtube.com/watch?v=mVsZIFiDD0o&feature=plcp
Steel brackets and strapping for parts shouldn't be a problem, provided it's well-insulated and won't conduct. Steel in the spark gaps isn't a huge problem, but you'll need to watch the surface of the contacts for damage. Sharp edges around "craters" caused by the sparks could prove to be a problem. Just keep it clean and smooth and you'll avoid energy loss.

another thing you might consider doing is cutting the primary in half and configuring the capacitors for double the capacitance/half the voltage.
I would NOT recommend that for several reasons. First, depending on the voltage of your capacitors, halving the voltage tolerance would be a bad idea. It's a good way to damage them. It would also reduce the efficiency of the coil. Even if the tank circuit is in perfect tune with the secondary, the coil won't work correctly unless the capacitor is properly matched to the transformer. In an AC Tesla coil setup, the spark cap discharges every half cycle. If the capacitor and transformer aren't properly matched, the capacitor might not have enough time to fully charge before being discharged into the primary. This will make the coil much less efficient and it will not work properly.

From prior discussions, I know that lokey's transformer is a 15Kv 30mA. According to the formula,
, where C is the matching capacitance, Z is the impedance (transformer voltage/transformer current), and Fl is the line frequency (60 Hz), the tank capacitor value he needs is about 5.3nF. Removing too much will make the coil operate incorrectly. Overall, I would get a capacitance as close to the calculated one as possible and go from there.

Tesla coils are very touchy--one thing even slightly off can make the entire thing not work. Patience is key ;)
 
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#4
I think he has 8.6nF so it would probably make sense to put the 4 caps in series-parallel rather than parallel.

might need more turns on the primary though, idk.
 

DerStrom8

Super Moderator
Most Helpful Member
#5
I think he has 8.6nF so it would probably make sense to put the 4 caps in series-parallel rather than parallel.

might need more turns on the primary though, idk.
He originally had 9.15nF, with four caps in parallel. After removing one, which he did earlier, he's left with approximately 6.9nF. He could probably get even closer to the necessary value by taking another one off, bringing it to 4.6nF, and have a slightly longer primary to keep the tank circuit at its resonant frequency. Putting the four caps in series-parallel would only give him about 2.3nF, which is nowhere near enough.

His primary is definitely long enough to allow him to tap it wherever needed. I don't think he'll need to make it longer at all.
 

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