Hi Tim,
If I may jump in here. My personal advice would be to go ahead and build the biggest thing that you can with what you have available. Reason being is - and trust me on this - I promise that once you've built your single 15/60 NST driven coil and coaxed it to optimal performance, you WILL wanna go BIGGER! This "build a bigger one" syndrome seems to be a pretty much universal ailment amongst the coiling community, so you may as well prepare yourself for this almost certain outcome on the front end :-) I started with NST driven coils nearly 20 years ago and my most aggressive coil to date is the Green Monster, which stands nearly 8 ft. tall with its 12" x 56" topload and is driven by a properly ballasted 10 kVA, 14,400 volt pole pig! And it is quite an attention getter with its bright, fat and quite noisy ground striking ~12 ft. sparks, but being a classic ARSG driven coil, its "guts" ain't too portable! (Estimate the total weight of the entire system, including the massive ~1200 lb. control panel, to be in the the neighborhood of 1600 lbs!) But if fund$ were no object and space and available electrical service would allow, I'd probably build an even bigger one! ;-) Actually, my control panel is beefy enough to drive an even larger coil than the Green Monster, but I'd need access to professional high voltage laboratory facilities to house and run such a beast ;-))
Anyway, good luck with your project, whatever size that you decide to go with.
David
Timothy Gilmore <tdg8934@xxxxxxxxx> wrote:
>Gary,
>
>Sounds like a pretty scary adventure veering off from the plans I have
>which indicate simple things such as just adding more capacitance. I think
>what I will do first is get a working single NST tesla coil first
>(15kv/60mA) and using the 2nd NST as a backup incase the first ever gets
>fried. If it looks like the design is stable than perhaps later on I will
>take on a 2 NST new design. Its been 35 years since I built my first and so
>much great development has happened and new ideas learned by the smart
>people here and other places in the Tesla Coil world. Thanks again for your
>insight and the others here that make this such a fun hobby.
>
>Tim
>
>On Fri, Feb 20, 2015 at 8:02 PM, Gary Lau <glau1024@xxxxxxxxx> wrote:
>
>> The only reason to have transformers be identical is a matter of
>> aesthetics. As long as the output voltage is remotely similar, one can mix
>> France, Jefferson, whatever, flavors of NST's, if the phasing is correct,
>> and you'll know immediately if it's wrong. It's _nice_ to have them
>> identical but functionally unnecessary.
>>
>> > There would be a lot more changes than just caps and gaps.
>>
>> I would like to amplify the above point. Assuming you want to do
>> everything needed to extract the maximum arc length from the additional
>> power at your disposal, repeat over and over - Bigger is Better. You'll
>> want a larger top load, and you'll want a taller secondary to space the top
>> load farther from the primary to avoid strikes to it. The larger top load
>> and secondary will require a significantly larger primary, not just another
>> couple of turns. I ended up building a 2-layer primary to keep
>> the dimensions sane. Higher inductances and lower frequencies are all
>> good!
>>
>> Also, a 15/120 power supply is probably going to push the limits of what a
>> static gap can handle. You didn't mention what you're planning for a gap
>> but you might wish to consider a rotary. I highly recommend the propeller
>> gap configuration - http://www.laushaus.com/tesla/sync_gap.htm If you're
>> thinking about a synchronous rotary, the capacitor size needs to be much
>> higher than for a static gap, and will require comparably more primary
>> inductance.
>>
>> And, a 15/120 power supply is going to pull a LOT of juice from the wall -
>> you'll want to make sure you have an adequate PFC capacitor to minimize
>> current draw. My single 15/60 pulls in excess of 20A with a sync rotary
>> and 240uF of PFC caps.
>>
>> Bottom line - you should plan from day 1 what the final configuration is
>> going to be - you'll not be able to go back and forth with 1 or 2 NST's.
>>
>> Regards, Gary Lau
>> MA, USA
>>
>>
>>
>>
>>
>> On Fri, Feb 20, 2015 at 1:32 PM, Timothy Gilmore <tdg8934@xxxxxxxxx>
>> wrote:
>>
>> > Great videos on Phasing (both parts 1 and 2). I will watch those again
>> when
>> > ready to set up.
>> >
>> > On Fri, Feb 20, 2015 at 9:36 AM, John Paul Grippa <pupman@xxxxxxxxxxxx>
>> > wrote:
>> >
>> > > There is a great video from the Geek Group on YouTube that explains how
>> > > this works extremely well. It will also give some good tips on how to
>> > > ensure proper phasing. Check it out!
>> > > https://www.youtube.com/watch?v=KSlQjw9OPG4
>> > >
>> > >
>> > > > Date: Fri, 20 Feb 2015 08:26:17 -0600
>> > > > From: tdg8934@xxxxxxxxx
>> > > > To: tesla@xxxxxxxxxx
>> > > > Subject: [TCML] Dual identical FRANCE neon sign transformers (15000v
>> > > 60mA each) in parallel
>> > > >
>> > > > I currently have a France NST at 15kv 60mA and built a nice jacobs
>> > ladder
>> > > > with it. Yesterday on eBay I found what looks to be identical model
>> NST
>> > > for
>> > > > a good price (no GFI). From what I have read about NST phasing,
>> having
>> > > > identical NSTs don't require testing the HV outputs and I should be
>> > able
>> > > to
>> > > > connect them up in parallel identically using the same sides. What a
>> > > jacobs
>> > > > ladder at 120mA would be! Anyway I'm assuming that I should start
>> > > building
>> > > > my tesla coil with 1 NST and when it works add the next NST in
>> parallel
>> > > and
>> > > > double the capacitors and change the tap on the primary. Does this
>> > sound
>> > > > like all I would need to do?
>> > > >
>> > > > Thanks - Tim
>> > > > _______________________________________________
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