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"I" / Rod core HV transformer for obtaining very high voltages

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Dr. Dark Current

Sat Oct 18 2008, 12:22PM

Registered Member #152 Joined: Sun Feb 12 2006, 03:36PM
Location: Czech Rep.
Posts: 3384

I was wondering about this:

(the actual transformer

)

How does it manage to run so well with just single "I" core, on 50Hz? There must be very big no-load inductive currents, right? Or it's not so bad?

I think this would be a neat way of winding HV transformers up to very high voltages, no secondary to core flashovers to worry about! You could wind the secondary as big as you would want (well not overly big as the outer layers won't be getting much V/turn).

Maybe this can be also brought to the solid-state world, get a big ferrite rod, wind a monster HV secondary on it, and drive at high frequency (>100kHz)?

I would like to hear your thoughts on this.

-J.M.

Erlend^SE

Sat Oct 18 2008, 12:29PM

Registered Member #1565 Joined: Wed Jun 25 2008, 09:08PM
Location: Norway
Posts: 159

When looking at the picture of the actual transformer, the "chassis" can very possibly be iron, and work as magnetic return, while your transformer drawing doesn't mention it.

Just reminds me of what I have read about ignition coil contruction.

Just my fast guess :)

Dr. Dark Current

Sat Oct 18 2008, 01:10PM

Registered Member #152 Joined: Sun Feb 12 2006, 03:36PM
Location: Czech Rep.
Posts: 3384

Erlend^SE wrote ...

When looking at the picture of the actual transformer, the "chassis" can very possibly be iron, and work as magnetic return, while your transformer drawing doesn't mention it.

Just reminds me of what I have read about ignition coil contruction.

Just my fast guess :)

I'm pretty sure it's plastic, at these voltages (the xfmr is 170kV) a metal case would be unusable, not mentioning that the case would be too thin to carry noticable amount of magnetic flux..

Antonio

Sat Oct 18 2008, 01:32PM

Registered Member #834 Joined: Tue Jun 12 2007, 10:57PM
Location: Brazil
Posts: 644

An easy way to obtain imperfect coupling and natural current limiting. Really, probably needs some extra turns to keep the primary inductance high, but maybe not too many, as the magnetic field at the center of the core will not change much with or without a closed core.

rp181

Sat Oct 18 2008, 01:59PM

Registered Member #1062 Joined: Tue Oct 16 2007, 02:01AM
Location:
Posts: 1529

what language is the site in? i so want to translate it.

Dr. Dark Current

Sat Oct 18 2008, 02:35PM

Registered Member #152 Joined: Sun Feb 12 2006, 03:36PM
Location: Czech Rep.
Posts: 3384

rp181 wrote ...

what language is the site in? i so want to translate it.

Steve Conner

Sat Oct 18 2008, 03:09PM

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

Yes, there will be large inductive currents. Power factor correction capacitors would help, but the guy who built these transformers has something like 200A 3 phase supply, so he probably doesn't care about the magnetizing current. Or the fact that he just erased his neighbour's whole collection of VHS movies.

It works great in the solid-state world. In fact you can even get rid of the ferrite, and you have this thing called a "Solid-state Tesla coil". You should try making one some day

Dr. Dark Current

Sat Oct 18 2008, 03:43PM

Registered Member #152 Joined: Sun Feb 12 2006, 03:36PM
Location: Czech Rep.
Posts: 3384

Steve McConner wrote ...

It works great in the solid-state world. In fact you can even get rid of the ferrite, and you have this thing called a "Solid-state Tesla coil". You should try making one some day

well, I did actually make one (:P), but because of the large magnetizing currents and high frequency, I want to make something not just for shooting arcs into the air, with bigger power output and maybe lower voltages, in smaller package

Would there be any advantage in terms of magnetizing current of using a laminated I core instead of ferrite one?

Coronafix

Sat Oct 18 2008, 08:49PM

Registered Member #160 Joined: Mon Feb 13 2006, 02:07AM
Location: Melbourne, Australia
Posts: 938

I wondered if it was possible to remove the secondaries off of MOTs and put them on a single rod, this
diagram gives that some hope, although it would undoubtedly be better to wind a new one.

Dr. Dark Current

Sun Oct 19 2008, 03:04PM

Registered Member #152 Joined: Sun Feb 12 2006, 03:36PM
Location: Czech Rep.
Posts: 3384

Coronafix wrote ...

I wondered if it was possible to remove the secondaries off of MOTs and put them on a single rod, this
diagram gives that some hope, although it would undoubtedly be better to wind a new one.

Probably not, even if you remove only the I part of the core and leave everything on the E core, it will draws tens of amps on the primary without load.
Maybe if you had a nice big and long laminated rod core, the cross-section of a MOT core and length lets say 50cm, you could probably fit a few MOT secondaries on it, but who has such core on his disposal

...

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