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What To Do With All My NST's

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KeeDx3

Wed Aug 02 2017, 06:06AM

Registered Member #61435 Joined: Thu Jan 19 2017, 06:46AM
Location:
Posts: 25

teravolt wrote ...

most nst have 2 secondaries out of phase. If you want to combine there power you can phase and parallel the outputs. As your current grows you can draw the arc out further. If you do this combine transformers of the same voltages. In this way you can deliver more power to your tesla

Ah, yeah I have a Jacob's Ladder with two 15/30's in parallel. Hopefully it's soon-to-be four, which might become my eventual TC power supply, if I find two more matching (identical make/model) 15/30 NST's (I'm OCD like that).

Luckily, the NST's I've paralleled in the past have been identical, so I simply oriented them the same way and bonded everything straight across.

Here's a question I've been curious about; having to do with voltage and current in TC use. Would you rather have two 15/30's in parallel or four 12/30's? What would give superior performance - double the amps or a few extra thousand volts?

Sulaiman

Wed Aug 02 2017, 08:00AM

Registered Member #162 Joined: Mon Feb 13 2006, 10:25AM
Location: United Kingdom
Posts: 3140

The part of an sgtc that gets the biggest hammering is the spark gap,
for a given power, higher voltage means lower current so less SG wear.
(and wider SG gaps which foul less quickly)

Higher voltage means lower primary capacitance for a given power,
so a higher impedance coil is required ... which needs longer copper.
Conversely, as you can find 25 ft. tubing easily, paralleling NSTs will mean higher capacitance, hence lower inductance ... fewer turns.
The stress on the SG will be greater and overall efficiency will be a little lower.
You will need a powerful flow of air through the spark gap (my preference) or a (Richard Quick / TCBOR) multiple series SG, also preferably with airflow.
(a poorly performing SG has a loud fuzzy arc, a well performing SG has thin VERY LOUD arcs)

To me, a small coil with long arcs'n'sparks looks more impressive than a much larger TC with slightly longer sparks'n'arcs,
There is an empirical formula for spark length, it is a good target;
(spark length in inches) = 1.7 x Power
(from memory, John Freau, 60 Hz, synchronous rotary SG, kilowatts)

e.g. 225 Watts input, target = 1.7" x SQRT(225) = 1.7" x 15 = 25.5"
... good luck !

In answer to your specific question,
2x [15/30] = 900 VA, 4x [12/30] = 1440 VA so should give ('ideally' 26.5%) longer sparks,
if other components are suitably rated.

If you continue along the TC direction then it would be better to start a new thread in Tesla Coils rather than continue here in High Voltage.

To me a TC is more impressive than a J-L of similar power,
but a well made J-L is impressive, maybe more profitable to make and sell ?

radiotech

Fri Aug 04 2017, 08:09PM

Registered Member #2463 Joined: Wed Nov 11 2009, 03:49AM
Location:
Posts: 1546

If you are experimenting, and using domestic 120/240 circuits be aware of some factors.

The year is 2017. Circuits are loaded with electronic devices now. They can be damaged by
transients introduced by arcing loads.

Magnetic core NSTs have low unloaded power factor. This means the current may
exceed the circuit capacity without drawing any power. Anything else on the circuit
with load of variable power factor i.e. motor might set up circulating currents,
and may experience speed variations if you draw heavy arcs.

In past (younger) days I blew out all the light bulbs and a few TV sets,
when a high voltage supply arced over on just one branch circuit. I have been
licensed as a Master Electrician for 43 years. From this I can tell you, inspectors
will hunt you down if you cause mayhem.

Your grounding scheme is very important.

Ideally, an experiment powering up multiple transformers might be safer
run off a generator, far from anything costly. A 5 or 10 kW portable unit,
outdoors would be ideal.

Interesting book~~ 1935, reprinted by Lindsay.

KeeDx3

Sat Aug 05 2017, 05:46AM

Registered Member #61435 Joined: Thu Jan 19 2017, 06:46AM
Location:
Posts: 25

Thanks for the heads up - especially since I have been considering paralleling as many NST's as my breakers will handle.

I know that a lot of Tesla Coilers use line filters when driving NST coils. Is that type of protection sufficient? Let's say I had 4 NST's in parallel. I could use one big line filter or even one small one per transformer. Maybe even running the filters in parallel/redundantly?

As you can see, I *really* don't want to replace any computers ;).

radiotech

Sat Aug 05 2017, 06:44PM

Registered Member #2463 Joined: Wed Nov 11 2009, 03:49AM
Location:
Posts: 1546

On the safety/liability side, the determinants are :

Were the devices used in accordance with their certified applications?

If used as a part of an assembly, i.e. a neon sign, that sign will be certified as a unit. Once
the sign is installed, then any work or modifications are the responsibility of
the sign company.

An exception would be a Professional Engineer, acceptable to local authorities,
designing special applications using the transformers.

E.B.C.

Sun Oct 28 2018, 08:12AM

Registered Member #61923 Joined: Tue Nov 21 2017, 03:27PM
Location: NW Montana USA
Posts: 11

I know its been well over a year since you posted this thread but i figured that it could'nt hurt to at least ask if you might have any of those NSTs left that you'd consider selling? I live in NW Montana & am fairly new to coiling but would realy like to try using an NST instead of the mot power supplies ive built myself. Please let me know, id relally appreciate it. Thank you.

Charles73

Wed Nov 28 2018, 06:09AM

Registered Member #61343 Joined: Mon Dec 05 2016, 05:38AM
Location:
Posts: 18

E.B.C. wrote ...

I know its been well over a year since you posted this thread but i figured that it could'nt hurt to at least ask if you might have any of those NSTs left that you'd consider selling? I live in NW Montana & am fairly new to coiling but would realy like to try using an NST instead of the mot power supplies ive built myself. Please let me know, id relally appreciate it. Thank you.

I do! A few dozen 12/30's and a handful of 15/30's. I'll send you a PM.

Edit: Sorry, KeeDx3 is my old account that I seem to have locked myself out of.

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