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Registered Member #477
Joined: Tue Jun 20 2006, 11:51PM
Location: Seattle, WA
Posts: 546
jmartis wrote ...
Just to clear things up, a 15/60 NST will NEVER output 900W or anything close that! The 60mA is short-circuit current, the maximum output power will be achieved with 1/2 output voltage but with the current also just at around 1/2 (guess) - so you will get about 250W out maximum.
Ok, so you're saying that a 15/60 is good for maybe 1.5-foot streamers (by the Freau equation)? It may be a simplification to say that a 15/60 is 900W, however simplifying a TC load down to a "short circuit" is much, much worse! I have seen folks get 3.5- and 4-foot streamers with a 15/60 NST. Working backwards from there (again, with the Freau equation) suggests a power in the 800-900W range. I really think the "short circuit" analogy is unworkable here.
Regarding the better performane with the MOTs cited in a prior post: My calculations are based on a 120bps break rate. It's quite possible the MOT coil is running with a higher break rate than that. That would make sense.
Registered Member #30
Joined: Fri Feb 03 2006, 10:52AM
Location: Glasgow, Scotland
Posts: 6706
Jmartis's argument only holds for a resistive load. The capacitive load in a Tesla coil can partly cancel the ballasting inductance of the NST and make it deliver more power. Sometimes a lot more :o
Registered Member #160
Joined: Mon Feb 13 2006, 02:07AM
Location: Melbourne, Australia
Posts: 938
Kristian wrote ...
By voltage doubler I mean I put a MO cap in series with each HV output and put a couple of MO diodes across them. Should be 12,000V peak pulsed DC.
I was getting about 40" arcs with breakout point to grounded target using the NST power supply and .015uf cap. Without the breakout point I would get a few weak looking 2 foot streamers at a time. I'm getting about 42" arcs using the MOTs, but the arcs are much brighter and thicker. Without the breakout, the arks are numerous and about 3 feet with a few longer streamers breaking out every so often . As far as my observations go, the MOT supply is definitely out performing the NST supply.
Hi Kristian, Love the output on your coil! Can you clarify your schematic with a drawing or a pic, it doesn't sound like you are using a charging choke, is this right? How do the diodes and MO caps connect in the circuit? Impressed. Michael
edit/ Concerning the sucker gap, I believe this is the best performing static out there, not by experience yet, just through research of others sites.
Registered Member #991
Joined: Sun Sept 09 2007, 05:47AM
Location:
Posts: 6
Well, what gave me the idea of using the 2 MOTs without any voltage doubling was Greg's site http://hot-streamer.com/greg/ . He successfully did this, but with a sucker gap and a large cap.
Registered Member #611
Joined: Wed Mar 28 2007, 11:40PM
Location: Hudsonville, Michigan
Posts: 79
Goldsphere wrote ...
...Can you clarify your schematic with a drawing or a pic, it doesn't sound like you are using a charging choke, is this right? How do the diodes and MO caps connect in the circuit?
Registered Member #160
Joined: Mon Feb 13 2006, 02:07AM
Location: Melbourne, Australia
Posts: 938
and those two wires go straight to your tank circuit huh? very nice, I think I will try this with my large coil too...about a week off from completion. Kids are a time vacuum.
Registered Member #991
Joined: Sun Sept 09 2007, 05:47AM
Location:
Posts: 6
Just thought I'd post an update on my spark gap. The garage door opener motor is indeed synchronous, so I built the whole gap assembly tonight and gave it a test. Awesome results compared to what it used to be. about 28" arcs, and 24" streamers. I didn't do too much tuning, so I'll need to add another toroid and play with the primary a bit.
I still need to figure out a way to bypass the "fault protection circuit" on the transformers I have, because I can only apply power to the transformers for ~1 second before one transformer cuts its power.
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2 MOT supply
Ok, so you're saying that a 15/60 is good for maybe 1.5-foot streamers (by the Freau equation)? It may be a simplification to say that a 15/60 is 900W, however simplifying a TC load down to a "short circuit" is much, much worse! 
I have seen folks get 3.5- and 4-foot streamers with a 15/60 NST. Working backwards from there (again, with the Freau equation) suggests a power in the 800-900W range. I really think the "short circuit" analogy is unworkable here.
