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i have a circuit to be constructed, where i need to use PP pulse capacitors and i got my hands on Polyester capacitors, this is for pulse applications, im wondering if it could be used as a replacement, as the circuit is not functioning as it should and thats what i could narrow down the problem to be.

Thnx

Cheers

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  • \$\begingroup\$ Maybe instead of calling it a "pulse application" you could in fact state what it is and produce a circuit."i" is capitalized btw and polyester doesn't need to be. \$\endgroup\$
    – Andy aka
    Apr 20, 2015 at 21:29
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    \$\begingroup\$ Use polypropylene for any application that calls itself "pulse". Better yet, go by the manuf's spec sheets. The WIMA site is a good place to start. There are construction details that are often used in pulse caps and not common in others. \$\endgroup\$
    – Robert Endl
    Mar 21, 2017 at 15:00

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Dielectric absorption (DA) is much (5-10x) higher for polyester capacitors as compared to polypropylene, so losses will be higher, which could cause problems.

There may be other differences in construction that would affect pulse applications, however they are not inherent to the choice of dielectric.

Edit: I don't think the capacitors you show are necessarily suitable- the pulse current could be very high, which those parts are not designed for (my second original paragraph above). Consequence could be slow or rapid destruction of the capacitors as the metallization blows off the mylar and perhaps shorting of the plates.

There are other types of capacitor easily available which could be substituted but I think I'll let others suggest them. This seems like a pretty dangerous project.

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  • \$\begingroup\$ if this could help as i dont know that much about capacitor specificities i should be using this capacitor (eu.mouser.com/ProductDetail/Vishay-BC-Components/BFC238320683/…), while what i found locally was (wima.com/EN/mks4.htm) is it a suitable replacement? \$\endgroup\$
    – M A
    Apr 20, 2015 at 20:42
  • \$\begingroup\$ It is not specified for pulse applications, so it is clearly not a direct replacement. It may or may not fail depending on the actual circuit requirements. \$\endgroup\$
    – Spehro Pefhany
    Apr 20, 2015 at 20:48
  • \$\begingroup\$ this is the actual circuit (ctmuzzleloaders.com/ctml_experiments/electric_ignition/…) it can be viewed at the bottom of the page the capacitor in question is marked as C2 \$\endgroup\$
    – M A
    Apr 20, 2015 at 22:04
  • \$\begingroup\$ would ceramic capacitors do the trick? \$\endgroup\$
    – M A
    Apr 21, 2015 at 16:47
  • \$\begingroup\$ @MA The very same manufacturer makes pulse-rated capacitors, which have a different (self-healing) internal design. So, why don't you use those instead? However, I will say that I don't think this project sounds very safe to attempt for someone not yet at the level of being able to specify suitable components. So, BE CAREFUL! \$\endgroup\$
    – Oleksandr R.
    Apr 21, 2015 at 17:46

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