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Re: [TCML] crusher capacitor design
Ken wrote:
List,
I have managed to acquire 72 X EPCOS 500V- capacitors. I want to make a
coin crusher using these capacitors. Would it be best to wire these in
sets of three of 24 in series for 12000 volts? I first tried it with
three sets of 24 in parallel for 1500 volts for a great bang, but no
crush. Is the high voltage needed in order to make it crush?
Here is a link to my other 6000 joule coin crusher that I would like to
parallel these new capacitors with for a total of 20,000 joules.
http://kenscoil.com/coincrusher.htm
Thanks!
Ken
Hi Ken,
For good results, use a capacitor bank voltage of at least 5 - 6 kV in
order to overcome coil resistance and capacitor ESR. Higher voltages
will also work, but bank voltages above 20 kV may cause premature
turn-turn flashovers on the work coil. Capacitor internal construction
is important. You want caps with low ESR and low ESL, and the caps will
need to handle the expected peak current in order to survive thermal
stresses and magnetic forces. The "sweet spot" for minimal coin
distortion seems to be between 3000 - 8,000 joules (depending on the
coin), 100-300 uF, and bank voltages of about 7.5 - 15 kV.
Putting groups of caps in parallel reduces bank ESR, ESL, and peak
current/cap (all good), but you may need to connect more groups in
series to also reach the necessary bank voltage. Some caps may not
suitable for this application. Which EPCOS caps are you trying to use?
Since this is very off topic on the TCML, please contact me directly if
you need any further information or would like to discuss further.
Bert
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