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Easy 340Vdc capacitor bank and charger

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Fusion

Tue Nov 21 2006, 10:52PM

Registered Member #354 Joined: Thu Mar 30 2006, 10:12AM
Location:
Posts: 55

I used a 100W lamp before a diode bridge in order to power my 4x470uF capacitor bank directly from 220V supply.
It is very nice because when cold the lamp has 40ohms and hot is 400 ohms, so the bank charges in only 12 seconds. If the lamp does not switch off is because there is a short circuit. I do not need a fuse.
In the second image you can see the elastic-switch (similar to used by tesladownunder)

In the third image there is a plot of a wire discharge test (I made 6).
It is very nice to work with few volts because probes widstands it.

I have not the blast photo because I couldnt catch it, but there was very few light so perhaps I generate lots of UV rays so I am working now in a UV probe.

I calculated that current reached 23kA

Tesladownunder

Thu Nov 23 2006, 02:43PM

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

Thats a sensible way to do things when you need to charge to mains voltage.
Even though you have a switch of clearly superior design (

), you won't be able to achieve 23,000A. Measuring these currents is not easy. Electrolytics discharge to peak in about 1ms if you look at Jason Rollette's capacitor bank and he achieves 100kA with a comparitively huge bank with big conductors.
I use a Rogowski coil to measure it.

You can't simply use a wire resistance to calculate current. I have generated 600V over about a foot of copper busbar and one heavy bolt largely from inductive rather than resistive effects.

Peter

Fusion

Thu Nov 23 2006, 09:39PM

Registered Member #354 Joined: Thu Mar 30 2006, 10:12AM
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Posts: 55

It is true is very difficult to measure current. I only had the voltage, but I discharged the whole 100 Joules capacitors to a 0.16mmx10mm wire in 24us (look to scope plot), and E=V*I*t , then 100 joule=340*I*12e-6 (I had taken time to fall to half voltage), then I=24000.

Look that I do not use wires, I used aluminium bars: Power is important but also the way how you use it

Now I have done an Ultraviolet sensor with its transimpedance amplifier:
Dibujo107

*** mod edit, image too big, 400 pixels width max please ***
Then I placed it in a copper tube with a hole in order to avoid RF:

Then I made a spark and had a plot but I am a very bad photographer:

I obtained a 700mV peak! thats corresponds to 8.42W of UV.
I surprised a lot because voltage was drop in only 12microseconds, but UV burst stayed up to 150us, so how it is possible that after copper wire blast there is still UV sending?. Sensor is OK because I tested it and frequency and voltage coverage was good. The only explanation I have is that copper atoms stored the great magnetic energy that could not be dissipated and released it as UV.

Marko

Thu Nov 23 2006, 09:49PM

Registered Member #89 Joined: Thu Feb 09 2006, 02:40PM
Location: Zadar, Croatia
Posts: 3145

Fusion: you should reduce your pics into links, anyone interested can see them by just one click.

You'l make mods angry by ruining forum format and slowing the loading down..

Simon

Fri Nov 24 2006, 11:15PM

Registered Member #32 Joined: Sat Feb 04 2006, 08:58AM
Location: Australia
Posts: 549

Yes, lamps make excellent current limiting for chargers. They're cheap and readily available for their power rating and, even better, their resistance drops as the current drops, as you mentioned.

Fusion

Mon Dec 11 2006, 09:13PM

Registered Member #354 Joined: Thu Mar 30 2006, 10:12AM
Location:
Posts: 55

And here are more plots. I made implosion of a glass and it was cut like butter: I read that glass has an ultimate yield strength of 50 gigapascals and it was taken only 59 joules from a 106 Joule capacitor bank. In last photo I measured an incredible peak of more than 120kW of Ultraviolet light burst. I had to remove the transimpedance amplifier and use UV sensor serially with a 100 ohm sensing resistor: as more current, less silicon!

Fusion

Mon Dec 18 2006, 01:59PM

Registered Member #354 Joined: Thu Mar 30 2006, 10:12AM
Location:
Posts: 55

Looking back the test photos I discovered a dry sonoluminiscent phenomena: see the violet sphere over the exploding wire. I have seen also at other tests.

Tesladownunder

Mon Dec 18 2006, 11:40PM

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

Fusion wrote ...

It is true is very difficult to measure current. I only had the voltage, but I discharged the whole 100 Joules capacitors to a 0.16mmx10mm wire in 24us (look to scope plot), and E=V*I*t , then 100 joule=340*I*12e-6 (I had taken time to fall to half voltage), then I=24000.

Look that I do not use wires, I used aluminium bars: Power is important but also the way how you use it

I am having trouble understanding the 24us discharge. Could you confirm the scope readings and scale and what they represent. What are you reading the voltage of anyway. It doesn't look like an exponential decay curve. I suppose if each cap is 50nH then you have a 200nH setup. Which could explain it. Larger caps will increase this. If you had 500J at this inductance you would be able to crush cans.

Peter

ragnar

Tue Dec 19 2006, 04:40AM

Registered Member #63 Joined: Thu Feb 09 2006, 06:18AM
Location:
Posts: 1425

I'm not convinced that violet sphere isn't a camera artefact.

Steve Conner

Tue Dec 19 2006, 08:28AM

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

Yes, it looks like a lens flare to me too.

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