λ/2 magnifier
omegalabs, Thu Jun 12 2014, 02:04PMHello!
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 λ/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.
Re: λ/2 magnifier
Sulaiman, Thu Jun 12 2014, 05:22PM
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
Sulaiman, Thu Jun 12 2014, 05:22PM
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
Re: λ/2 magnifier
Hazmatt_(The Underdog), Fri Jun 13 2014, 03:40AM
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.
Hazmatt_(The Underdog), Fri Jun 13 2014, 03:40AM
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.
Re: λ/2 magnifier
omegalabs, Fri Jun 13 2014, 03:56PM
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.
omegalabs, Fri Jun 13 2014, 03:56PM
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.
Re: λ/2 magnifier
Mads Barnkob, Fri Jun 13 2014, 09:21PM
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 :)
Mads Barnkob, Fri Jun 13 2014, 09:21PM
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 :)
Re: λ/2 magnifier
Antonio, Fri Jun 13 2014, 11:41PM
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):
Antonio, Fri Jun 13 2014, 11:41PM
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):
Re: λ/2 magnifier
Steve Ward, Sat Jun 14 2014, 02:48AM
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.
Steve Ward, Sat Jun 14 2014, 02:48AM
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.
Re: λ/2 magnifier
omegalabs, Sat Jun 14 2014, 02:32PM
omegalabs, Sat Jun 14 2014, 02:32PM
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.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 :)
Re: λ/2 magnifier
Sulaiman, Sat Jun 14 2014, 09:05PM
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.
Sulaiman, Sat Jun 14 2014, 09:05PM
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.
Re: λ/2 magnifier
omegalabs, Mon Jun 16 2014, 11:44PM
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.
omegalabs, Mon Jun 16 2014, 11:44PM
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.
Re: λ/2 magnifier
omegalabs, Sat Aug 09 2014, 06:06PM
I have an idea to make the magnifier L1-L2 easier, but I would like to ask it first. Instead of helical L1 L2, probably a spiral L1 and L2 would be better in many cases (like a planar transformer), which can be done only in the magnifier conception. Coupling can be adjusted very easily, insulation between the 2 coils can be simply done by addig a lot of PE sheets for example. The outer end of the L2 should be the ground, and the inner end should be the HV output. Of course this means the center would be on a high potential, because of this, the L1 should be made with a bigger inner diameter. With this method someone can spare a lot of space, so the whole L1-L2 can be immersed in oil.
Also I realised, the twin 3phase magnifier must be driven by a DC resosnant charging circuit, there is no other way, as either I would need a big resistor, or the drop of the transformers must be very high.
So at this point it looks like this will be a 3 phase DC resonant λ/2 magnifier. This will be a nasty coil
omegalabs, Sat Aug 09 2014, 06:06PM
I have an idea to make the magnifier L1-L2 easier, but I would like to ask it first. Instead of helical L1 L2, probably a spiral L1 and L2 would be better in many cases (like a planar transformer), which can be done only in the magnifier conception. Coupling can be adjusted very easily, insulation between the 2 coils can be simply done by addig a lot of PE sheets for example. The outer end of the L2 should be the ground, and the inner end should be the HV output. Of course this means the center would be on a high potential, because of this, the L1 should be made with a bigger inner diameter. With this method someone can spare a lot of space, so the whole L1-L2 can be immersed in oil.
Also I realised, the twin 3phase magnifier must be driven by a DC resosnant charging circuit, there is no other way, as either I would need a big resistor, or the drop of the transformers must be very high.
So at this point it looks like this will be a 3 phase DC resonant λ/2 magnifier. This will be a nasty coil
Re: λ/2 magnifier
Steve Conner, Sun Aug 10 2014, 10:14AM
There is nothing fundamentally wrong with the bipolar magnifier idea.
A DC resonant charging circuit needs a rotary spark gap to define the break rate.
Also, if you are running off 3 phase power you don't need a smoothing capacitor on the DC bus. The ripple is low enough even without one.
Without the smoothing capacitor you don't need a de-Qing diode either, the rectifier bridge functions as one. However it may work out cheaper to use one in practice. If you use the rectifier for de-Qing, the diodes see twice the reverse voltage than if you used a separate de-Qing diode.
Steve Conner, Sun Aug 10 2014, 10:14AM
There is nothing fundamentally wrong with the bipolar magnifier idea.
A DC resonant charging circuit needs a rotary spark gap to define the break rate.
Also, if you are running off 3 phase power you don't need a smoothing capacitor on the DC bus. The ripple is low enough even without one.
Without the smoothing capacitor you don't need a de-Qing diode either, the rectifier bridge functions as one. However it may work out cheaper to use one in practice. If you use the rectifier for de-Qing, the diodes see twice the reverse voltage than if you used a separate de-Qing diode.
Re: λ/2 magnifier
omegalabs, Sun Aug 10 2014, 07:44PM
C1 is just a filter capacitor. Maybe I'll add a TVS chain near the bridge.
omegalabs, Sun Aug 10 2014, 07:44PM
C1 is just a filter capacitor. Maybe I'll add a TVS chain near the bridge.
Re: λ/2 magnifier
Dr. Dark Current, Tue Aug 12 2014, 04:07PM
With the coils and their surroundings not being 100% identical, you'll get slightly different resonant frequencies and one coil could be performing better than the other one. Though I'm not sure if this will be a problem in practice.
Dr. Dark Current, Tue Aug 12 2014, 04:07PM
With the coils and their surroundings not being 100% identical, you'll get slightly different resonant frequencies and one coil could be performing better than the other one. Though I'm not sure if this will be a problem in practice.
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