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omegalabs

Thu Jun 12 2014, 02:04PM

Registered Member #1521 Joined: Thu Jun 05 2008, 10:46AM
Location: Hungary
Posts: 128

Hello!
I would like to ask, has anyone ever built a half wave magnifier coil system? I was not able to find even one. I have this idea, because I need to build a half wave system, which can be assembled quickly, for circus performances (needs to be assembled after a different show). So I thought a normal twin tesla system, with separated primary-secondary is not good, it needs a lot of time to assemble the primary circuit, secondary ground, while the Î»/2 magnifier needs only 2 feedlines to the 2 extra resonators, and no separated RF ground, but I'm not sure if a system like this works, as I was not able to find a built one on the web.
The system will be around 9kVA, using 3 phase outlet.
But instead of a single 3 phase HV transformer, I asked a company to make 3 pieces of 1 phase, 3kVA HV transformer which will be connected Y:Y to the mains. I didn't calculated the parameters of the transformers yet, but their drop would be no less than 50%, their voltage probably between 5-10kV.

Sulaiman

Thu Jun 12 2014, 05:22PM

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

I'd swap the positions of C2 and the spark gap
for less hf voltage stress on the chokes and transformers.
I haven't tried this, conceptually it looks ok

Hazmatt_(The Underdog)

Fri Jun 13 2014, 03:40AM

Registered Member #135 Joined: Sat Feb 11 2006, 12:06AM
Location: Anywhere is fine
Posts: 1735

Your chokes will have to be vrey large, or your diodes will go POP!

You will need to check out the I_fs of the diodes to make sure they can handle the short circuit operation of the gap, or the peak current will kill them.

omegalabs

Fri Jun 13 2014, 03:56PM

Registered Member #1521 Joined: Thu Jun 05 2008, 10:46AM
Location: Hungary
Posts: 128

Diodes voltage will be a minimum of 3x Udc.
This is still just a concept, only with the most important elements, and approximate values.
Is there any reason why hasn't been a single one of this type built? I think it has more advantages than the widely used twin series primary TC.

Mads Barnkob

Fri Jun 13 2014, 09:21PM

Registered Member #1403 Joined: Tue Mar 18 2008, 06:05PM
Location: Denmark, Odense C
Posts: 1968

Twin series primary is easier to build, 3 phase mains is not that common in USA and generally there are not that many dual secondary coils made :)

Antonio

Fri Jun 13 2014, 11:41PM

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

No big problem in designing the coils and capacitances for this system. It can be obtained from a normal magnifier with parameters C1, L1, C2, L2, L3, C3, k12 by dividing L3 by 2 and multiplying C2 and C3 by 2. The transformer can be built with a primary coil around the center of the secondary coil, probably mounted horizontally for symmetry of the capacitances. For the normal design, look:

Some examples (from other discussion):

Steve Ward

Sat Jun 14 2014, 02:48AM

Registered Member #146 Joined: Sun Feb 12 2006, 04:21AM
Location: Austin Tx
Posts: 1055

3 phase mains is not that common in USA

While its not common to have 3 phase in your home in the US, almost every commercial/industrial building will have 3 phase 208V service (120V line-neutral voltage). Bigger buildings will have 480V, and occasionally you'll run into 240V 3ph.

omegalabs

Sat Jun 14 2014, 02:32PM

Registered Member #1521 Joined: Thu Jun 05 2008, 10:46AM
Location: Hungary
Posts: 128

Mads Barnkob wrote ...

Twin series primary is easier to build, 3 phase mains is not that common in USA and generally there are not that many dual secondary coils made :)

3 phase is a must in my case, because they only have 4kVA/phase, and it's not enough power. Otherwise 1ph would be easier, without this nasty rectifier bridge.

Sulaiman

Sat Jun 14 2014, 09:05PM

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

You may want to add inrush protection for the rectifier bridge and C1 circuit.
A common method is a resistor (e.g. 10 Ohm) between the bridge output and C1.
after the initial inrush a relay/contactor shorts out the resistor to allow full power dc.
You could use a manually operated or automatic system to operate the contactor.

omegalabs

Mon Jun 16 2014, 11:44PM

Registered Member #1521 Joined: Thu Jun 05 2008, 10:46AM
Location: Hungary
Posts: 128

Thanks for the infos.
Actually I found one system (looks like it's a bipolar magnifier, withouth the RF ground): video
I have a small 350W little magnifier, I'm going to try some calculations, and experiments with it. I'm thinking of a flat primary-flat driving coil (L1; L2-L3) would be interesting, easier to insulate with a simple thick plastic plate, and probably better coupling, in a smaller space.

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