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Author Topic: Defibrillator Capacitors for HV power supplies?  (Read 2257 times)
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K9MB
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« on: January 26, 2023, 08:03:28 PM »

I just remembered picking up some capacitors that were made to use in defibrillators and am wondering if anyone has used these in High voltage supplies?
They are rated at 6kv DC and are 36uF.
They use oil and polyurethane powder to form the insulation.
The data page for the CSI cap I have is below.
Is anyone familiar with them? Can they be used like the regular oil filled caps we use?

Any comments or advice is welcome.
73, Mike


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Patrick J. / KD5OEI
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« Reply #1 on: January 27, 2023, 12:07:09 AM »

These things grab me right off:
1.) energy storage capacitor.
2.) 'highest energy density'.
3.) lifespan of a quite low number of charge-discharge cycles.

So at max ratings no doubt it's running close to the edge, and is meant to be held there for only short times while waiting for the defibrillation process.

Perhaps it would be best, considering continuous charged duty for ham radio to derate the voltage to 50% (heard others suggest 75%). It's still a pretty large capacitor electrically. Thinking of its lifespan and or safety.

Best thing might be to contact the manufacturer and ask for the continuous voltage rating and the continuous 120Hz ripple current rating if they will give those specs.
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Radio Candelstein - Flagship Station of the NRK Radio Network.
K9MB
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« Reply #2 on: January 27, 2023, 12:58:23 AM »

These things grab me right off:
1.) energy storage capacitor.
2.) 'highest energy density'.
3.) lifespan of a quite low number of charge-discharge cycles.

So at max ratings no doubt it's running close to the edge, and is meant to be held there for only short times while waiting for the defibrillation process.

Perhaps it would be best, considering continuous charged duty for ham radio to derate the voltage to 50% (heard others suggest 75%). It's still a pretty large capacitor electrically. Thinking of its lifespan and or safety.

Best thing might be to contact the manufacturer and ask for the continuous voltage rating and the continuous 120Hz ripple current rating if they will give those specs.

Patrick,
Very good points. I have the same doubts.
Actually, I bought these last year and I actually wrote CSI and asked if they can be used as power supply filters and they answered “yes”.
I then ask them if I could use them to couple audio in a modulator and they said “no”…
I felt like I did when I went to a birthday party when I was nine and the little girl had an 8-Ball. It supposedly could answer the unanswerable, but it only answered with one or two words…. Needless to say- one word “yes” and “no” are not my cup of tea, so I was not any more sure than before.

The notes do say that heat will affect life and I wondered if limiting voltage might extend life.
Of course, you can see why I want it to work because they are rated at 6kv and 32uF in a very small package.

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w7fox
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« Reply #3 on: January 28, 2023, 11:00:02 AM »

I talked with a CSI engineer about this several years ago.  She said if I tried to use energy storage capacitors for power supply filtering they would probably fail.  However, lowering the voltage to one half to one third the rating would extend life considerably.  I used a pair of 53 microfarad 3.5 KV caps in series in a 2800 volt supply successfully for years.  I was surprised to see one used in a HV supply in the ARRL handbook running near the nameplate voltage.  I wonder how that turned out.  Good luck.
Best regards,
FOX
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K9MB
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« Reply #4 on: January 28, 2023, 02:57:56 PM »

I talked with a CSI engineer about this several years ago.  She said if I tried to use energy storage capacitors for power supply filtering they would probably fail.  However, lowering the voltage to one half to one third the rating would extend life considerably.  I used a pair of 53 microfarad 3.5 KV caps in series in a 2800 volt supply successfully for years.  I was surprised to see one used in a HV supply in the ARRL handbook running near the nameplate voltage.  I wonder how that turned out.  Good luck.
Best regards,
FOX

Hi FOX,
Thanks for that rundown.
Which year handbook were they in?
At 6kv rating, lowering it to 2500volts would answer the requirement.
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w7fox
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« Reply #5 on: January 28, 2023, 10:15:38 PM »

Mike,
The example is from the 1988 ARRL Handbook, page 30-51.  The capacitor in the article was a CSI 53 mf, 3.5 KV, 4W308T.  The exact part number I was discussing with the engineer.  It would be interesting to talk to one of the older chaps at league headquarters to see how it held up.
73
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K9MB
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« Reply #6 on: January 29, 2023, 12:32:24 AM »

Mike,
The example is from the 1988 ARRL Handbook, page 30-51.  The capacitor in the article was a CSI 53 mf, 3.5 KV, 4W308T.  The exact part number I was discussing with the engineer.  It would be interesting to talk to one of the older chaps at league headquarters to see how it held up.
73

Hi Fox,
Thanks for the reference. I just checked and that cap is still made by CSI.
The difference between this cap and the one I have is that this is a motor run cap and the one I have is made for a defibrillator as a storage cap. The motor run caps are in an environment where it is stressed all the time, so they are likely much tougher than the defib caps. I suspect that heat is the factor that shortens life.
Of course, theymay still be fine st reduced voltage.
73, Mike
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« Reply #7 on: February 23, 2023, 05:46:03 PM »

As I just posted in another thread, my 4x4-125A amp (construction beginning in 2004 as seen in the profile pic) uses a 56 uF, 4.2 KV defibrillator cap. I don't use it often but it's never broken down at 3-3.5 KV...
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K9MB
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« Reply #8 on: February 23, 2023, 06:23:08 PM »

As I just posted in another thread, my 4x4-125A amp (construction beginning in 2004 as seen in the profile pic) uses a 56 uF, 4.2 KV defibrillator cap. I don't use it often but it's never broken down at 3-3.5 KV...

Thanks for the note.
I don’t suppose that you have the make and model number for it?
I am gathering that as ling as you lower the voltage across them to about they may last a while.
However, when they go with several thousand volts across them and 56uF, it might not be pleasant event…😱😬😉😂
Maybe if I use some steel plate to make the enclosure….😉

They have an amazing amount of capacitance for their size, so it is tempting to try…
73, Mike
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