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Resonant tank circuit - capacitor help

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Hi, I'm building a parallel resonant tank. I need a capacitor bank capable of 500Vrms and 500Arms at about 5uF. The bank will be operating at frequencies between 30-80kHz. I have found some polyester metallised film capacitors on ebay; B81130 X2 MKP/SH 40/100/21/C 0.22uf 20% 275V
by epcos. What can each one take in terms of current.
I can create a bank rated at 550Vac at 5.5uF - my question is could this bank handle it and how much power would it dissipate. Also if it can handle 500Arms - what is the maximum it could handle.

thanks

Note: last week I asked a question about a coupling transformer - I have sorted it now, impedance on primary was too high.
 
Any polyester metallised film capacitors for this much current flow will overheat.

I would say the best bet is to look at A.C. motor oil filled run capacitors.
 
This will be a bank consisting of 100 of these capacitors, 50 sets in parallel, each set is two caps in series. Are you sure that they cannot handle 10A each.

oil filled capacitors would be far too large and expensive, I will be water-cooling my bank. I'm just unsure how much current they can take and how much power they would dissipate.
 
If you find the ESR of the caps, then you can make a calculation of the approximate power dissipated in the caps.

Otherwise you need to buy caps that are characterized for the current you need.
 
I think you will have problems pushing 10 to 12 Arms through these caps at 50 kHz. There will likely also be a problem with all the inductance of the wiring connections. You also have to deal with the 20% possible tolerance mismatch.

Look at page 8 of spec at https://www.electro-tech-online.com/custompdfs/2010/05/MKT_B32231.pdf

About 0.04 ohms Rs based on self resonance impedance. That is about 4 watts dissipation per cap.


**broken link removed**
 
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I think I can keep the inductance pretty low and isnt too much of a problem.

Dissipating 400W of power is quite a bit more than I expected though even with water cooling.

I can get a single capacitor for the job but it will cost me about £60, making a bank will cost me £20.

Can anyone suggest any cheap capacitor alternatives or any places in the UK that could supply me with old used but working induction heating capacitors?
 
I can get a single capacitor for the job but it will cost me about £60, making a bank will cost me £20.

Can anyone suggest any cheap capacitor alternatives or any places in the UK that could supply me with old used but working induction heating capacitors?

Can you provide a link to the single capacitor you've found that will do the job? Or, post a spec sheet? This is a single 5 µF capacitor that can handle 500A at 500V?

You don't want to use polyester capacitors for a job like this; metallized polypropylene is much better. See:

**broken link removed**

Especially have a look at the DC link capacitors.

But, I think the polypropylene capacitors will have too much capacitance.

You need a large number of mica transmitting capacitors in parallel.
 
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