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NST's in parallel

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LAN_403

Mon Mar 31 2008, 02:24AM

Registered Member #1415 Joined:
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Posts: 21

My tesla coil currently make 30 inch sparks with a 12kv 30ma NST. What would happen if I bought another transformer the same as mine and wired it in parallel? When I say "what would happen" I mean spark length

Spedy

Mon Mar 31 2008, 03:21AM

Registered Member #964 Joined: Wed Aug 22 2007, 12:39AM
Location: Stockton, CA
Posts: 134

If you just paralleled them, I;m pretty sure it would just increase current available, not voltage.

Mon Mar 31 2008, 04:01AM

Registered Member #1415 Joined:
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I realize that the voltage would stay the same, but does a larger amount of current passing through the primary coil induce more current into the secondary, thus causing a longer spark?

Ultra7

Mon Mar 31 2008, 04:12AM

Registered Member #1157 Joined: Thu Dec 06 2007, 12:11PM
Location: Houston, TX
Posts: 307

You'll gain some length and they will be brighter.
You will gain some 14 inches with the higher current.

Teslamap says at 12/30 you should have at least 36" sparks.
With the 12/60 you should have at least 42" sparks.

Just be sure you phase them properly if you decide to parallel them.

Also, keep your runs under 5 minutes to avoid damage to your NST's if you parallel them.

MOT_man

Mon Mar 31 2008, 04:20AM

Registered Member #1127 Joined: Mon Nov 19 2007, 12:08AM
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I have had some strange performance problems with a new NST placed parallel with my 12 kV 120mA 1.44 kW transformer. This one is a power factor corrected NST 12kV 60mA - when I run it off of the same circuit I can hear the transformer fighting with the gap of my tesla coil - yet when I run the transformer off of a separate circuit everything works fine - again its hook in parallel. I'm guessing its a phasing issue. Odd - never tried using power factor corrected NSTs before...

Mon Mar 31 2008, 04:30AM

Registered Member #1415 Joined:
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how do you phase them properly

Ultra7

Mon Mar 31 2008, 05:06AM

Registered Member #1157 Joined: Thu Dec 06 2007, 12:11PM
Location: Houston, TX
Posts: 307

SteveC wrote ...

how do you phase them properly

Read this entire article, it has everything.
How to get NST's for almost free, how to crack them, how to parallel them. . .

Remember that paralleling them will probably kill them in extended runs.
Although I've yet to kill one (touches wood) by paralleling, I still try to keep my runs below 5 minutes.
My Variac starts to buzz at around 4 minutes, and my ARSG gets red hot, so I start my shutdown at about 4:30 into the run.

HV Enthusiast

Mon Mar 31 2008, 12:58PM

Registered Member #15 Joined: Thu Feb 02 2006, 01:11PM
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Posts: 3068

If you just add another NST in parallel, you are most likely going to KILL your NSTs. What will happen is that because you didn't change the primary capacitor size, it will build up very large voltages (now that you have twice the current) and these transients will kill your NSTs.

You can add another NST in parallel, but you have to make other changes as well.

MOT_man

Sun Apr 06 2008, 06:28AM

Registered Member #1127 Joined: Mon Nov 19 2007, 12:08AM
Location:
Posts: 139

Well, I changed a few things on my Tesla Coil today - just the 3.25 " demo coil. I ramped up the primary capacitance to 64 nF and then phased 3 X 12kV 60 mA NSTs on the same circuit... then replaced my topload with a much larger one. 65" thus far not tuned... its getting close to peak output... I'm aiming for 70".

I'll be sending you video - but here is pict of my coil running the dual NSTs 12kV 120mA - 32 nF cap... smaller topload...
Strikes were 50" at peak --- that streamer goes far off the screen ... I'll upload another picture soon
-

I'll give an update - just finished the tuning and I cranked out another 12.5" inches. So now I'm up to 70" output ---- .... okay so I must be at near peak output now.... guess the gap needs to be better quenched....

My 14.4 kV PT coil is much easier to run... and MOTs were effortless... but NEONs .... I don't really enjoy them much. So much RF protection - phasing issues.... ;)

MOT_man

Mon Apr 07 2008, 03:07AM

Registered Member #1127 Joined: Mon Nov 19 2007, 12:08AM
Location:
Posts: 139

Ultra7 wrote ...

SteveC wrote ...

how do you phase them properly

Read this entire article, it has everything.
How to get NST's for almost free, how to crack them, how to parallel them. . .

Kill an NST by paralleling them... no, not in my experience. Buy hooking the capacitors up across the transformers - yes you'll kill the NSTs for sure - or by not using a terry filter. I've seen some big NST banks - 12 kV 300 mA / 600mA --- pretty stupid if you ask me, but it does its job.

SORRY ABOUT THE DOUBLE POST - WON'T HAPPEN AGAIN.... my mistake.

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