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stirring up SSTC trouble

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Kolas

Sun Feb 26 2006, 02:05AM

Registered Member #102 Joined: Thu Feb 09 2006, 08:15PM
Location: Raleigh, NC
Posts: 169

now what defines an sstc?
air core?

what would it be called if i stuck a ferrite core inside the former?

I will not accept the term flyback mind you. Keep in mind there is No magnetic loop.

Kolas

HV Enthusiast

Sun Feb 26 2006, 02:16AM

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

[quote]
now what defines an sstc?
air core?
[/quote]

A Tesla Coil is an air-core resonant transformer. A Tesla coil excited by solid state means is an SSTC.

wrote ...

what would it be called if i stuck a ferrite core inside the former?

Well, it wouldn't be a Tesla coil since it isn't an air core anymore. It would be just a transformer.

wrote ...

I will not accept the term flyback mind you. Keep in mind there is No magnetic loop.

Uh, no. There is ALWAYS a magnetic loop.

Tesladownunder

Sun Feb 26 2006, 02:23AM

Registered Member #10 Joined: Thu Feb 02 2006, 09:45AM
Location: Bunbury, Australia
Posts: 1424

Hmmmmm...
What about oil filled secondaries? (I am planning one in my multilayer coil). Perhaps a more correct definition would be non-ferromagnetic cored rather than air cored

My first "Tesla coil" had a ferrite core (but still sneaked it into the ** add your Tesla coil here ** thread). See below.

Kolas

Sun Feb 26 2006, 02:34AM

Registered Member #102 Joined: Thu Feb 09 2006, 08:15PM
Location: Raleigh, NC
Posts: 169

sure, magnetic loop...
i mean a compleated loop, by Means of a core

im setting out to show that a reaonant pulse coil is a viable means of generating super hv output
of course it will be set up similarly as an sstc
kolas

vasil

Sun Feb 26 2006, 11:10AM

Registered Member #229 Joined: Tue Feb 21 2006, 07:33PM
Location: Romania
Posts: 506

Use a ferrite toroid on the top. It will be stil an air core transformer, but the magnetic properties of the secondary will change

Steve Conner

Sun Feb 26 2006, 11:20AM

Registered Member #30 Joined: Fri Feb 03 2006, 10:52AM
Location: Glasgow, Scotland
Posts: 6706

Flyback cores have an air gap, so there would be no essential difference. I would say you had made a flyback, or one of those electric ignitors you find in gas boilers. I once dismantled one of those and it consisted of a Tesla coil like thing with a ferrite rod core.

I'll be surprised if you can get higher voltage with a ferrite core than with an air core. The ferrite does improve efficiency, but by being there it eats into the clearances you need around the output terminal, up to 30" for 1MV.

Oil insulation makes that much less of a problem, and most industrial HV/HF equipment (where they actually care about efficiency as opposed to spark size) uses oil-filled transformers with ferrite cores.

Kolas

Mon Feb 27 2006, 05:33AM

Registered Member #102 Joined: Thu Feb 09 2006, 08:15PM
Location: Raleigh, NC
Posts: 169

ok, assuming i can stand off the votlages created, will it work?
im thinking yes
thats why i have a 6" long ferrite rod coming my way
kolas

Dr. Shark

Wed Mar 01 2006, 01:47PM

Registered Member #75 Joined: Thu Feb 09 2006, 09:30AM
Location: Montana, USA
Posts: 711

What you are creating will be very similar to a car ignition coil, only that you will be able to drive it at reasonably high frequencies without core losses becoming a problem. Seeing how people get 5" arcs out of car iginition coils this should be good for high voltages. But keep in mind that you loose the resonant voltage rise you have in a TC if you have tight coupling, so you probably need to pulse it for a big inductive kick on the primary. Car ICs have about 100 primary turns and a 1:200 turns ratio (I am guessing here), so using a normal SSTC secondary might work out well.

Good luck!

Sulaiman

Wed Mar 01 2006, 07:45PM

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

For a ferrite core one significant problem is maximum flux is limited
by saturation
or
by flux limits due to ferrite heating at high frequency.

If you do the sums for your ferrite you will probably find about 10Vrms per turn is the most it will handle, even with 0.2mm wire thats only 7,500 Vrms maximum;
so all sinewave systems (Tesla Coil etc) will be limited to this value.

More volts/turn can be achieved using the same core and coil
in 'flyback' operation.

P.S. I have a 1" x 1" x 20" ferrite core for just this purpose.

Dr. Shark

Thu Mar 02 2006, 09:12AM

Registered Member #75 Joined: Thu Feb 09 2006, 09:30AM
Location: Montana, USA
Posts: 711

I dont think you can easily saturate a core with a 6" airgap, even if I cant come up with any numbers to quantify this. Sulaiman, you seem to have the formulas, why dont you go trough the maths?

The 10V/turn figure sounds more appropriate for the ferrite without any airgap at all.
I think the distincion between "sinewave systems" and flybacks can be put best as "transformers" vs. "coupled inductors". If you read up on forward converter topologys you will find that a flyback is nothing but a boost converter with a two windings for additional step-up and isolation. TCs are, IMHO, on the "inductor" end of the spectrum, as most of the voltage gain is not from turns ratio, but from resonance.

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