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How to charge a 10kV 5uf Cap

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GammaRay

Sun Dec 08 2013, 10:18PM

Registered Member #5323 Joined: Fri Jun 15 2012, 02:14PM
Location:
Posts: 104

I have a 10kV @ 5uf Maxwell Capacitor. I'd like to charge it to just under 10kV, but don't own a suitable HV power supply.
Any suggestions how this cap could be charged up? (Yes, I will be careful!). Thank you in advance.

klugesmith

Sun Dec 08 2013, 10:59PM

Registered Member #2099 Joined: Wed Apr 29 2009, 12:22AM
Location: Los Altos, California
Posts: 1716

Couldn't be much simpler if you can get a 15 kV neon sign transformer
without secondary ground fault protection.
Then add two HV diodes to make a full wave rectifier.
One end of yout capacitor will be tied to the NST center tap and to safety ground.
I have used that configuration for my 52 uF 20 kV Aerovox capacitor, up to 6 kV.
Be sure yolu have a trustworthy HV meter before running close to the capacitor rating.

How are you planning to discharge the cap?
A direct short circuit while charged to max V will probably abuse the capacitor by exceeding its max current rating. Do you a have an ESL rating?

With your cap you can make a dandy can crusher,
which I bet will want on the order of 10 turns in the coil. 25 joules of stored energy is enough to start making a detectable indentation.

Sulaiman

Mon Dec 09 2013, 06:37PM

Registered Member #162 Joined: Mon Feb 13 2006, 10:25AM
Location: United Kingdom
Posts: 3141

250 Joules .... about the same as a defibrilator

How to charge? .... depends upon how fast you want it charged/re-charged.

Extremely Slow;
One terminal to earth, the other via insulated conductor to a metalic structure 100m up in the air
Van de Graaff generator
1000 freshly shampooed fluffy kittens with nylon combs

Quite Slow;
mains multi-stage voltage-multiplier with 1N4007 diodes and 10nF capacitors

Slow;
Flyback from crt (initial charging may cause core saturation due to low output voltage)

Quick;
MOT transformer, diodes and capacitors multi-stage voltage multiplier

I like NST (or OBIT) due to inherent current limiting
but with 5uF @ 10kV power supply safety is not the main concern.
'Ideal' could be a 7kV rms transformer....peak = 10kV so no need for cutoff/timer

Patric

Mon Dec 09 2013, 06:40PM

Registered Member #2899 Joined: Wed Jun 02 2010, 06:31PM
Location: Deinze, Belgium
Posts: 255

Sulaiman wrote ...

250 Joules .... about the same as a defibrilator

How to charge? .... depends upon how fast you want it charged/re-charged.

Extremely Slow;
One terminal to earth, the other via insulated conductor to a metalic structure 100m up in the air
Van de Graaff generator
1000 freshly shampooed fluffy kittens with nylon combs

Quite Slow;
mains multi-stage voltage-multiplier with 1N4007 diodes and 10nF capacitors

Slow;
Fluback

GammaRay

Mon Dec 09 2013, 09:30PM

Registered Member #5323 Joined: Fri Jun 15 2012, 02:14PM
Location:
Posts: 104

I do own a Allanson Neon Transformer 12kV @30ma. 2 pictures attached. However, the label reads "Sec. Mid-Point Referenced Sec. Ground-Fault Protection MPG" Is this transformer any good for charging up my 10kV cap?

1386624582 5323 FT159541 High Voltage Transformer 035 25

1386624582 5323 FT159541 High Voltage Transformer 058 30

klugesmith

Mon Dec 09 2013, 09:56PM

Registered Member #2099 Joined: Wed Apr 29 2009, 12:22AM
Location: Los Altos, California
Posts: 1716

12 kV NST is ideal -- you can charge to over 8 kV, without risk of overcharging the capacitor.

In my experience, the SGFP will shut the transformer down if you operate with a full-wave-rectifier.
Get a couple of diodes (the ones in MWO's will do) and try it. Use a variac if available.
How are you supposed to put the transformer in "BYPASS SERVICE MODE" listed on the case?
Is there a push button, to bypass the SGFP for a limited time?

In models where the SGFP module is not potted in solid dielectric, you can physically bypass it.
At least two models are presented in this forum thread:

Please show us what's under the lid of -your- transformer.

One more time: what are you using to measure the high voltage?

[edit]
Let's see a picture of your transformer with a properly connected 3-wire power cord.
At least if you plan to use it for something more engaging than a Jacob's Ladder.

GammaRay

Tue Dec 10 2013, 03:52PM

Registered Member #5323 Joined: Fri Jun 15 2012, 02:14PM
Location:
Posts: 104

There is a push button (unlabeld) at the top right. The lid is riveted on, won't be able to open to show the inside without drilling the rivets out. Since my meters don't register up to 10kV, I may have to resort to calibrating a spark gap to spark at around 8 or 9 kV as a crude measurement. Does this transformer lend itself to the suggestion above about simply applying two HV microwave diodes in order to charge my 10kV cap?? Would be great if it is that simple. Looking forward to hearing back.

1386690718 5323 FT159541 High Voltage Transformer B 005 25

klugesmith

Wed Dec 11 2013, 01:09AM

Registered Member #2099 Joined: Wed Apr 29 2009, 12:22AM
Location: Los Altos, California
Posts: 1716

I sent you a PM about this.

How many more minutes or hours, and/or dollars, are you willing to spend on this exercise?

What are you going to do with the 5 uF capacitor, after you succeed in charging it to kilovolts?
More to the point, how do you plan to discharge it in a controlled way?

Shrad

Wed Dec 11 2013, 09:11AM

Registered Member #3215 Joined: Sun Sept 19 2010, 08:42PM
Location:
Posts: 780

GammaRay wrote ...

Since my meters don't register up to 10kV

do you know about resistive dividers?

Thomas W

Wed Dec 11 2013, 03:15PM

Registered Member #3324 Joined: Sun Oct 17 2010, 06:57PM
Location:
Posts: 1276

klugesmith wrote ...

How do you plan to discharge it in a controlled way?

^
The most important part, one time i charged up a 1kJ Capacitor.... couldnt work out how to dischaged it, dropped a metal bar on it (bad idea, my ears rang for some time 'cause i was in a small room)

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