"Ignoramus27088" wrote in message
. ..
The seller was wrong in describing them as 22 VOLT capacitors. They
are 22 KILO volt capacitors. (the seller is Fermilab).

This is kinda a sad commentary on the kind of people they'll hire at Fermilab
these days, no?

I don't know the proper care and feeding of such high energy storage
capacitors, but when I've seen people working with them they always carried a
long (about 6') wooden stick with a shorting strap (about 1"x6") on top to
always ensure the caps were discharged before they touched them.

On Thu, 30 Mar 2006 19:52:44 GMT, Ignoramus27088 wrote:

The procedure would be
- connect everything
- put on hearing protection
- turn on the franceformer
- disconnect franceformer with remote disconnect.
- turn face away, short the steel flats using broomhandle
- hear BOOM
- describe testing in the ebay ad

Something in the dim recesses of my mind is telling me that a "boom"
discharge would be bad for caps. I'd rather, as a buyer, see a one,
five, and ten minute voltage check, and know that it was discharged
through a power resistor. Those, I can help you with.

Last time I did a boom with a capacitor, it broke the "broomhandle" AND
the capacitor terminal leaving a nice leak hole...
And that was ONLY 300V, but 10uF.
I think the resistor way is safer.

OBones wrote:

Last time I did a boom with a capacitor, it broke the "broomhandle" AND
the capacitor terminal leaving a nice leak hole...
And that was ONLY 300V, but 10uF.
I think the resistor way is safer.

For some reason I'm not seeing the original post, so I'll tack this on
here--if their condition is unknown it would be a good idea to have a solid
barrier between you and the capactor when charging and discharging the
first time, and do one at a time..

Also, have good ventilation in the test area--if one blows you probably
don't want to breathe what comes out of it.

--
--John
to email, dial "usenet" and validate
(was jclarke at eye bee em dot net)

Discharging caps that way can ruin the cap. Just turn off the supply or
apply a resistor load. The internal plates violently move - ripping themselves up.

You get away with it - smile - sell it - it blows up when used. Not a happy day.

Martin

Martin Eastburn
@ home at Lions' Lair with our computer lionslair at consolidated dot net
NRA LOH & Endowment Member
NRA Second Amendment Task Force Charter Founder
IHMSA and NRA Metallic Silhouette maker & member


Ignoramus27088 wrote:
On Thu, 30 Mar 2006 11:44:24 -0800, Joel Kolstad wrote:

"Ignoramus27088" wrote in message
m...

The seller was wrong in describing them as 22 VOLT capacitors. They
are 22 KILO volt capacitors. (the seller is Fermilab).

This is kinda a sad commentary on the kind of people they'll hire at
Fermilab these days, no?


Indeed.


I don't know the proper care and feeding of such high energy storage
capacitors, but when I've seen people working with them they always carried a
long (about 6') wooden stick with a shorting strap (about 1"x6") on top to
always ensure the caps were discharged before they touched them.


OK, I think that we are up to something here.

The test setup that I may try is as follows:

- 9kV franceformer feeding the cap, with remote disconnect leading to
the HV pole
- Wires from the cap connected to two junk steel flats, all set safely
apart
- A shorting stick (also made of junk steel) with a wooden broomhandle

The procedure would be

- connect everything
- put on hearing protection
- turn on the franceformer
- disconnect franceformer with remote disconnect.
- turn face away, short the steel flats using broomhandle
- hear BOOM
- describe testing in the ebay ad

i


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Ignoramus27088 wrote:
On Thu, 30 Mar 2006 11:44:24 -0800, Joel Kolstad wrote:

"Ignoramus27088" wrote in message
m...

The seller was wrong in describing them as 22 VOLT capacitors. They
are 22 KILO volt capacitors. (the seller is Fermilab).

This is kinda a sad commentary on the kind of people they'll hire at
Fermilab these days, no?


Indeed.


I don't know the proper care and feeding of such high energy storage
capacitors, but when I've seen people working with them they always carried a
long (about 6') wooden stick with a shorting strap (about 1"x6") on top to
always ensure the caps were discharged before they touched them.


OK, I think that we are up to something here.

The test setup that I may try is as follows:

- 9kV franceformer feeding the cap, with remote disconnect leading to
the HV pole
A FranceFormer is a neon sign transformer, and definitely AC.
- Wires from the cap connected to two junk steel flats, all set safely
apart
- A shorting stick (also made of junk steel) with a wooden broomhandle

Hmmm, better be sure that stick is dry, clean and free of cracks in the
wood.
The procedure would be

- connect everything
- put on hearing protection
- turn on the franceformer
- disconnect franceformer with remote disconnect.
- turn face away, short the steel flats using broomhandle
- hear BOOM
- describe testing in the ebay ad
The boom might be quite impressive, as these are probably Marx generator
pulse discharge caps, and may have a current capacity of tens
of thousands of amps.

Jon

On Thu, 30 Mar 2006 21:26:26 -0600, Jon Elson wrote:
The boom might be quite impressive, as these are probably Marx generator
pulse discharge caps, and may have a current capacity of tens
of thousands of amps.

Yes, they say "DISCHARGE CAPACITOR" on the dataplate. They probably
were using them to power high power lasers. One of my acquaintainces
worked there on lasers at some point.

i

Ignoramus27088 wrote:
On Thu, 30 Mar 2006 23:01:22 +0200, OBones wrote:

Last time I did a boom with a capacitor, it broke the "broomhandle" AND
the capacitor terminal leaving a nice leak hole...
And that was ONLY 300V, but 10uF.
I think the resistor way is safer.


ok... what would be a good resistor... I figure, 1 megohm or so should
be just about right, RC of these 1 uF caps would be about 1
second. Discharging most of about 40 joules in a couple of seconds.

i

Well, let's see. P = 22 kV squared / 1E6 = 484 Watts.
Well, that isn't so amazing, but I don't know where you will
find a 1 Meg Ohm resistor with a 500 W rating and a 22 KV
voltage rating.

Jon

I have a bunch of 1N4007 diodes (1000v rated). If I put, say, 20 of
them in series, would that be sufficient to rectify 9,000 VAC safely?
I have read some articles discussing that since leakage amps are not
identical, that I need to put resistors in parallel with them. If so,
these need to also be 1kV rated resistors, right?

If not, would anyone have a suggestion for a 30 mA rectifier for 9
kVAC?

thanks

i

Ignoramus27088 wrote:
- A shorting stick (also made of junk steel) with a wooden broomhandle


At the olde ion beam lab, we used pvc or fiberglass handles, not wood.
Wood would be a poor choice. And a resistor (a big honking 50W resistor,
which the Lab's EE assured inquiring minds WOULD NOT be surviving a full
discharge - this is a safety tool used to approach supposedly discharged
capacitors and be damn sure that they are discharged before you touch
them, not a device to discharge them through, other than that last few
hundred volts which is more than enough to kill you...) Speaking of
which, you never want to store these things without having them shorted,
solidly. A HV capacitor which is just sitting around can collect a
lethal mount of static. If they did not come to you pre-shorted, someone
was not behaving responsibly at fermilab.

It's been a few decades, so I don't recall the precise size of the banks
involved, but even the little bitty ones made a bang of unholy
proportions, and spewed a fine dose of X-rays around the discharge area
as well. Nobody but nobody got anywhere near the things when they were
charged, and they lived in tanks full of transformer oil to keep the
terminals from arcing over in the air. The big one (many capacitors)
sounded a bit like dropping a V-8 engine from 3 stories, and vaporized
the electrodes every time it was fired.

If the capacitors are oil-filled, and they probably are, you need to
verify (or make the seller verify) that they are free of PCBs, or you
are in for a world of trouble disposing of them in any way. They should
not have sold them if they were, but you need to be sure.

In short, you really do not want to test these to anywhere near their
capacity. Your HV supply is not suitable, and if it was, you'd be
looking at a world of hurt without investing a few thousand in test
gear. You could test them in a low-voltage RC circuit, I suppose, but
for all actual purposes which they might be used, it's not very relevant.

--
Cats, coffee, chocolate...vices to live by

On Fri, 31 Mar 2006 04:02:07 GMT, Ecnerwal wrote:
Ignoramus27088 wrote:
- A shorting stick (also made of junk steel) with a wooden broomhandle


At the olde ion beam lab, we used pvc or fiberglass handles, not wood.
Wood would be a poor choice. And a resistor (a big honking 50W resistor,
which the Lab's EE assured inquiring minds WOULD NOT be surviving a full
discharge - this is a safety tool used to approach supposedly discharged
capacitors and be damn sure that they are discharged before you touch
them, not a device to discharge them through, other than that last few
hundred volts which is more than enough to kill you...) Speaking of
which, you never want to store these things without having them shorted,
solidly. A HV capacitor which is just sitting around can collect a
lethal mount of static. If they did not come to you pre-shorted, someone
was not behaving responsibly at fermilab.

Thank you. I will pick them up on Tuesday early morning, I believe
that they are all shorted.

Well, here's a picture of the data plate, courteously emailed to me by
the seller:

http://igor.chudov.com/tmp/cap.jpg

Do you thikn that it has PCBs?


In short, you really do not want to test these to anywhere near their
capacity. Your HV supply is not suitable, and if it was, you'd be
looking at a world of hurt without investing a few thousand in test
gear. You could test them in a low-voltage RC circuit, I suppose, but
for all actual purposes which they might be used, it's not very relevant.


Thanks... I will think about this...

i

According to Ignoramus6399 :

Well, here's a picture of the data plate, courteously emailed to me by
the seller:

http://igor.chudov.com/tmp/cap.jpg

Maxwell Labs caps are really nice quality pulse discharge
capacitors.

Do you thikn that it has PCBs?

Hmm ... It says "impregnant MIPB" which sounds like something
different from PCBs. You might check whether they are still in
business, and ask them.

And these *might* actually surivive a dead-short discharge --
but it is still kinder to them to not do that.

Enjoy,
DoN.

--
Email: | Voice (all times): (703) 938-4564
(too) near Washington D.C. | http://www.d-and-d.com/dnichols/DoN.html
--- Black Holes are where God is dividing by zero ---

Ignoramus6399 wrote:
I have a bunch of 1N4007 diodes (1000v rated). If I put, say, 20 of
them in series, would that be sufficient to rectify 9,000 VAC safely?
I have read some articles discussing that since leakage amps are not
identical, that I need to put resistors in parallel with them. If so,
these need to also be 1kV rated resistors, right?

If not, would anyone have a suggestion for a 30 mA rectifier for 9
kVAC?

According to http://www.pupman.com/listarchives/1.../msg00143.html
"Use a MOT diode: typically they are 9kV 450mA and very cheap."
Apparently MOT means microwave oven transformer. Note, the 9kV RMS
AC of your Franceformer presumably peaks at about 13kV, so you would
need a variac on its input if using a single 9 kV diode. Also see
http://www.pupman.com/listarchives/1.../msg00309.html in same
thread, which implies that obvious tubes like 1B3 won't handle 30 mA.

-jiw

"Ignoramus6399" wrote in message
...
I have a bunch of 1N4007 diodes (1000v rated). If I put, say, 20 of
them in series, would that be sufficient to rectify 9,000 VAC safely?

Nah- 9kVAC is 12.7kV peak, call it 15kV peak. The rectifier has to stand
off full voltage on the backswing, so you need 30kV diodes, minimum. 40 or
50kV would be even nicer.

If you make a doubler (which uses diodes of the same rating, but produces
twice the output voltage) you can test the capacitors at a bit over rated
voltage (maybe 26kVDC, 118% of ratings). All the caps I've bought are rated
for 150 or 200% of rated voltage for some time, though that doesn't mean
these are.

If you bring up the voltage slowly, through a resistor or variac perhaps,
you can monitor it (assuming you get a voltage probe) and stop right at 22kV
or so.

I have read some articles discussing that since leakage amps are not
identical, that I need to put resistors in parallel with them. If so,
these need to also be 1kV rated resistors, right?

Yeah, but conversely, I recall reading an article which stated that modern
diodes are avalanche rated, meaning that if the voltage across one diode
increases to say, rated PIV, current starts going up (it looks like a really
high voltage zener diode), pulling it back into balance.

Capacitors across the diodes were also recommended, but today's diodes are
more rugged to pulse and avalanche conditions (we've come a long way from
"top hat" diodes!) so this isn't necessary either.

If not, would anyone have a suggestion for a 30 mA rectifier for 9
kVAC?

Could rip the diodes out of a few TV sets/monitors. Or use the flybacks
themselves, LOL.

Tim

--
Deep Fryer: a very philosophical monk.
Website: http://webpages.charter.net/dawill/tmoranwms

On Fri, 31 Mar 2006 05:16:04 +0000, (DoN.
Nichols) Gave us:

According to Ignoramus6399 :

Well, here's a picture of the data plate, courteously emailed to me by
the seller:

http://igor.chudov.com/tmp/cap.jpg

Maxwell Labs caps are really nice quality pulse discharge
capacitors.

Do you thikn that it has PCBs?

Hmm ... It says "impregnant MIPB" which sounds like something
different from PCBs. You might check whether they are still in
business, and ask them.

And these *might* actually surivive a dead-short discharge --
but it is still kinder to them to not do that.


With those caps, it would be kinder to all elements involved,
including and perhaps even particularly the person causing the short.

On Fri, 31 Mar 2006 00:33:12 -0600, Tim Williams wrote:
"Ignoramus6399" wrote in message
...
I have a bunch of 1N4007 diodes (1000v rated). If I put, say, 20 of
them in series, would that be sufficient to rectify 9,000 VAC safely?

Nah- 9kVAC is 12.7kV peak, call it 15kV peak. The rectifier has to stand
off full voltage on the backswing, so you need 30kV diodes, minimum. 40 or
50kV would be even nicer.

Tim, I lost you a little bit here, sorry. Are you saying that I need
single 30kV diodes and that putting 1 kV diodes in series is
unsuitable? Or are you saying that twenty 1,000 V diodes is not
enough?


I have read some articles discussing that since leakage amps are not
identical, that I need to put resistors in parallel with them. If so,
these need to also be 1kV rated resistors, right?

Yeah, but conversely, I recall reading an article which stated that modern
diodes are avalanche rated, meaning that if the voltage across one diode
increases to say, rated PIV, current starts going up (it looks like a really
high voltage zener diode), pulling it back into balance.

Yes, tat would be very nice.

i

"Ignoramus27098" wrote in message
...
so you need 30kV diodes, minimum. 40 or 50kV would be even nicer.

Tim, I lost you a little bit here, sorry. Are you saying that I need
single 30kV diodes and that putting 1 kV diodes in series is
unsuitable? Or are you saying that twenty 1,000 V diodes is not
enough?

30-50kV PIV "diode", collectively. You can make that "diode" out of as many
1N4001 diode*s* as you need.

Tim

--
Deep Fryer: a very philosophical monk.
Website: http://webpages.charter.net/dawill/tmoranwms

On Fri, 31 Mar 2006 09:44:00 -0600, Tim Williams wrote:
"Ignoramus27098" wrote in message
...
so you need 30kV diodes, minimum. 40 or 50kV would be even nicer.

Tim, I lost you a little bit here, sorry. Are you saying that I need
single 30kV diodes and that putting 1 kV diodes in series is
unsuitable? Or are you saying that twenty 1,000 V diodes is not
enough?

30-50kV PIV "diode", collectively. You can make that "diode" out of as many
1N4001 diode*s* as you need.

Thanks, now I understand a little better. I will soon make a stack of,
say, 30 1N4007 diodes. That would let me test the capacitors with 13
kV.

i

Martin H. Eastburn wrote:

Discharging caps that way can ruin the cap. Just turn off the supply or
apply a resistor load. The internal plates violently move - ripping
themselves up.

Given that they were made by Maxwell and sold to
Fermilab, they are probably spec'ed for pulse
discharge. That said, I'd not want to be on the
same city block when iggy crowbars them.

Putting a hard metalec short across them will no
doubt blow half the terminal away, create a deafening
blast and generate a nice EMP pulse. There's no
way I'd do it.

In article ,
Ignoramus6399 wrote:

Do you thikn that it has PCBs?

Likely not, based on that label - it's simply something that, if you
have ever had to deal with, you NEVER make assumptions about from that
point on, because they were so widely used when they were in vogue.

--
Cats, coffee, chocolate...vices to live by

Ignoramus27098 wrote:
On Fri, 31 Mar 2006 09:44:00 -0600, Tim Williams wrote:
"Ignoramus27098" wrote in message
...
so you need 30kV diodes, minimum. 40 or 50kV would be even nicer.
Tim, I lost you a little bit here, sorry. Are you saying that I need
single 30kV diodes and that putting 1 kV diodes in series is
unsuitable? Or are you saying that twenty 1,000 V diodes is not
enough?
30-50kV PIV "diode", collectively. You can make that "diode" out of as many
1N4001 diode*s* as you need.

Thanks, now I understand a little better. I will soon make a stack of,
say, 30 1N4007 diodes. That would let me test the capacitors with 13
kV.

i

Did something like that about 40 years ago. In our case we had to
bridge each diode with a small capacitor and large resistance resistor
because when seeing the reverse voltage, they did not all turn off fast
enough.

On Fri, 31 Mar 2006 18:53:25 GMT, Rich256 wrote:
Ignoramus27098 wrote:
On Fri, 31 Mar 2006 09:44:00 -0600, Tim Williams wrote:
"Ignoramus27098" wrote in message
...
so you need 30kV diodes, minimum. 40 or 50kV would be even nicer.
Tim, I lost you a little bit here, sorry. Are you saying that I need
single 30kV diodes and that putting 1 kV diodes in series is
unsuitable? Or are you saying that twenty 1,000 V diodes is not
enough?
30-50kV PIV "diode", collectively. You can make that "diode" out of as many
1N4001 diode*s* as you need.

Thanks, now I understand a little better. I will soon make a stack of,
say, 30 1N4007 diodes. That would let me test the capacitors with 13
kV.

i

Did something like that about 40 years ago. In our case we had to
bridge each diode with a small capacitor and large resistance resistor
because when seeing the reverse voltage, they did not all turn off fast
enough.

Hm... Were you trying to rectify a 60 Hz sinewave?

i

On Fri, 31 Mar 2006 19:05:12 GMT, Ignoramus27098 wrote:
On Fri, 31 Mar 2006 18:53:25 GMT, Rich256 wrote:

Did something like that about 40 years ago. In our case we had to
bridge each diode with a small capacitor and large resistance resistor
because when seeing the reverse voltage, they did not all turn off fast
enough.

Hm... Were you trying to rectify a 60 Hz sinewave?

Well, first thing you need is a big capacitor...

Ignoramus27098 wrote:
On Fri, 31 Mar 2006 18:53:25 GMT, Rich256 wrote:
Ignoramus27098 wrote:
On Fri, 31 Mar 2006 09:44:00 -0600, Tim Williams wrote:
"Ignoramus27098" wrote in message
...
so you need 30kV diodes, minimum. 40 or 50kV would be even nicer.
Tim, I lost you a little bit here, sorry. Are you saying that I need
single 30kV diodes and that putting 1 kV diodes in series is
unsuitable? Or are you saying that twenty 1,000 V diodes is not
enough?
30-50kV PIV "diode", collectively. You can make that "diode" out of as many
1N4001 diode*s* as you need.
Thanks, now I understand a little better. I will soon make a stack of,
say, 30 1N4007 diodes. That would let me test the capacitors with 13
kV.

i

Did something like that about 40 years ago. In our case we had to
bridge each diode with a small capacitor and large resistance resistor
because when seeing the reverse voltage, they did not all turn off fast
enough.

Hm... Were you trying to rectify a 60 Hz sinewave?

i



Both rectifying 400 Hz and use as a series diode in a resonant charging
circuit. Actually I was using 1 ampere silicon rectifiers which were
not fast enough. All it takes is one not turning off fast enough.

Rich256 wrote:
Ignoramus27098 wrote:
On Fri, 31 Mar 2006 18:53:25 GMT, Rich256 wrote:
Ignoramus27098 wrote:
On Fri, 31 Mar 2006 09:44:00 -0600, Tim Williams
wrote:
"Ignoramus27098" wrote in
message
...
so you need 30kV diodes, minimum. 40 or 50kV would be even
nicer.
Tim, I lost you a little bit here, sorry. Are you saying that I need
single 30kV diodes and that putting 1 kV diodes in series is
unsuitable? Or are you saying that twenty 1,000 V diodes is not
enough?
30-50kV PIV "diode", collectively. You can make that "diode" out
of as many
1N4001 diode*s* as you need.
Thanks, now I understand a little better. I will soon make a stack of,
say, 30 1N4007 diodes. That would let me test the capacitors with 13
kV.
i

Did something like that about 40 years ago. In our case we had to
bridge each diode with a small capacitor and large resistance
resistor because when seeing the reverse voltage, they did not all
turn off fast enough.

Hm... Were you trying to rectify a 60 Hz sinewave?

i



Both rectifying 400 Hz and use as a series diode in a resonant charging
circuit. Actually I was using 1 ampere silicon rectifiers which were
not fast enough. All it takes is one not turning off fast enough.

I don't remember just what we ended up using. I think it was about
..001u and 10 Meg across each diode.

Another problem was that a few diodes had bad junctions and couldn't
take the current. When you put 30 of them in series the probability of
getting a bad one is pretty high. Had to weed them out first.

According to Ignoramus27098 :

[ ... ]

Thanks, now I understand a little better. I will soon make a stack of,
say, 30 1N4007 diodes. That would let me test the capacitors with 13
kV.

You can make 30KV from a single 1KV 60 HZ transformer, with
enough diodes and capacitors. The basic circuit of a voltage multiplier
is:

(AC)---+--)|-+------+--)|--+-----(DC)
| | | |
\---/ --- \---/ ---
\ / / \ \ / / \
--- /---\ --- /---\
| | | |
(G)-)|--+-----+-)|---+------+

That one is enough for a 4X multiplication of the voltage. Keep
adding pairs of diodes and capacitors and you keep adding voltage
multiplications -- and losing current capacity.

1 KV AC is 1.414 KV DC peak, times 4 gives you 5.656 KV just
with this simple circuit. At work, we used fairly small assemblies
potted in epoxy to get 45 KV (three 15KV taps from a 1KV P-P input.

But -- it might take nearly forever to charge your caps.

Enjoy,
DoN.
--
Email: | Voice (all times): (703) 938-4564
(too) near Washington D.C. | http://www.d-and-d.com/dnichols/DoN.html
--- Black Holes are where God is dividing by zero ---

"Jim Stewart" wrote in message
...
Martin H. Eastburn wrote:

Discharging caps that way can ruin the cap. Just turn off the supply or
apply a resistor load. The internal plates violently move - ripping
themselves up.

Given that they were made by Maxwell and sold to
Fermilab, they are probably spec'ed for pulse
discharge. That said, I'd not want to be on the
same city block when iggy crowbars them.

Putting a hard metalec short across them will no
doubt blow half the terminal away, create a deafening
blast and generate a nice EMP pulse. There's no
way I'd do it.



I worked in a medical laser research group. We had 2u odd caps @ 10kv+ as
part of a home brew laser supply. Before working on it we'd double check the
caps were disharged in case the discharge resistors had failed.

A couple of PVC pipes 2m long with a 12" length of heavy neon sign cable
linking them, a couple of M4 screws were stuck through the ends.

When the caps were charged it was like a gun going off - very sharp bang, it
usually bought people out of offices all down the hallway. You never stood
behind whoever had the rods in case you got a reacting elbow in the face.

r.

Iggy, does that transformer output alternating current or
direct current?

--Winston

On Sat, 01 Apr 2006 13:08:16 -0800, Winston wrote:

Iggy, does that transformer output alternating current or
direct current?

AC, as it turns out.

i

DoN. Nichols wrote:
Do you thikn that it has PCBs?

Hmm ... It says "impregnant MIPB" which sounds like something
different from PCBs. You might check whether they are still in
business, and ask them.

http://www.gaep.com/frequently-asked-questions.html

IPB, IPBP, MIPB = isopropyl biphenyl

MIPB is mono-isopropyl-biphenyl

Might be current stuff. Google can turn up more...



Thomas