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FrozenGate by Avery

BIG capacitor bank

Oh it made some bangs alright, this time the caps made sure the transformer died. I think I'll go back to my old transformer now...

I pulled that core out of a kodak x-ray machine, so idunno.
 





Even with the 30A diode - how come?

Seems that there is something amiss - did the 30 amp diode fail as well?
 
Yes. I think the transformer tossed out a lot more volts than expected when it started going into parasitic oscillations.
 
What you might want to do is underwind the transformer by 100 or so turns, and see how much you can charge your cap up to.

I've now redone my board so a transformer fits on it (from RS components - core/bobbin/former).

Also is your tranny gapped?

I hope mine doesnt go bang - I dont like non deliberate bangs LOL :)
 
I tossed it; the thing was all carbon.

I took my other transformer and wound a primary on the same side as the secondary. The caps charge quite fast, bout as fast as the now-dead transformer. However it requires a 1/4" gap otherwise it starts with the parasitics. I think I need a new driver...
 
If you were in Aus I'd donate some IRf540's for your driver.

Well, I could send you one of my PCB's and a pair of mosfets to get you started. My PCB is untested, but based mainly on uzzors2k's 50W cap charger.

I've checked, checked, and triple checked everything is correct, the only additions I have made are an LM7805 to power an LED meter, and a second voltage divider, which can be utilised for charging 450v caps in series. You'll just need to change a sense resistor to drop it to 700V cutoff instead of 900V. If your only interested in charging to one particular voltage, you can omit the switch, second resistor and trimpot, and utilise a wire link to bypass the switch.

Free of course, I have 10 boards coming as of tomorrow/thursday (tuesday/wednesday in US/Canada). It wont cost much to post one to you. :)
 
Have you remembered to place a high power resistor in serie of the loading branch of the circuit ?

Capacitors have the bad abitude to act as a short-circuit, when they are subject to peaks, and the same happens when you try to charge a discharged bank with high voltage ..... ESPECIALLY if a big capacitors bank ..... technically, is the same as turn on your charging circuit with the output short-circuited, and for that value, this may go for seconds, not milliseconds (KABOOM)

Is not for decoration, that all the professional high power circuits have a power resistor (or a power resistor paralleled with a SCR triggered from the bank voltage, or also a power PTC) in serie between the transformer and the capacitors banks ;)
 
Got some samples yesterday.

LT3751 cap charger IC from linear technology, and Coilcraft GA4560 (I think) transformer.

If I can solder these tiny beasts (the IC), I should be able to easily build another 450V cap charger thats pretty darn small, and can charge at 42A! :)

May as well try - cant knock back free parts :)
 
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I hope you know that switching with only one fet will create A LOT of heat. LOTs, and at 42A you better have one hell of a water cooled heatsink.

That's why people use bridge circuits.
 
I've had it with mosfets, so I'm doing it old skool now.

http://uiu.me/tzz.jpg

* 3 stage CW, should have supplied 509V but gives 890V.
* Isolation transformer on the bottom, entire HV side is floating so I won't die if I touch either (but not both) wires.
* Relay on both the input and output.
* Interchangable lamp lets me limit charging power, and as the tungsten cools its resistance lowers, greatly reducing the RC time constant and charging the bank at near constant power.
* 30 ohm output resistor so I don't fry the diodes when the high voltage cw dumps into the possibly low voltage cap bank.700V / 30 = 23A (less than the diodes' Ifsm of 30A).

Next step, the contactor.
 
Hehe you have your contactor, and my puck SCR just turned up - Time to learn how to fire one of these things "forcefully" so it doesnt tunnel :)

I also got word my boards just shipped - YAY!
 
Well you will soon correct?

You are leaps and bounds in front of me, at least you have heard some bangs and snaps from your cap bank - mines still sitting in a box waiting to be put together.

I'm one of these people who saves up all the parts until I'm ready to assemble. Heres the latest round of bits to arrive :)

attachment.php


Top left is my not so big, but still capable puck SCR - time to work out how to mount it, along with its 1000-2000KG clamping force. Right of that is the 0-200V meter - I've already worked out a voltage divider for it so I can operate my bank up to 1.5Kv, assuming I decide on 1.35kv with 3 caps in series. Mind you I wont be exceeding 1.35Kv, the divider just gives me the 1.5Kv range.

Below that, the sloping case to be used for the remote console, so operator (me) isnt near ground zero :)

All sitting on top of a box full of 10 2400uf 450V capacitors, and 3 baggies full of assorted components for the project. Needed now is SCR clamp (not important), PCB's and little heatsinks.
 

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vk2fro said:
..... time to work out how to mount it, along with its 1000-2000KG clamping force. .....
Click to expand...

If you don't have its own clamp, you can improvisate "sandwich style" ..... the SCR in the middle, then a pair of plates (copper is better, but also aluminium will work), a bit larger than the SCR and long at least the double (so you have the space for drill and thread holes for the cable termination rings), and thick 4 or 5 mm, one for each side ..... then a pair of pieces of plexiglass at least 5mm thick, a pair of cm more large than the plates, then a pair of steel plates or bars with screws on the corners (ofcourse larger than the plexiglass) ..... it will work, just don't eat it ( stupid "sandwich related" word joke, i know :p :D)
 
It will probably ruin my teeth anyway - too crunchy :P

thanks for the advice HIMNL9

I was thinking a similar thing, but using blank pcb as the seperator (I have 4 huge bits of it here). Basiclly its like a circuit board with all the copper removed.

Until I work out a clamp and a circuit to hard switch the SCR, a rat trap with a pair of contacts will be my makeshift switch :)
 
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