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[SOLVED] Cap tolerance values

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Zak28

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Are capacitor tolerance ratings applicable to both voltage and capacitance or just one of them?

I search around couldn't find anything.
 

Applying tolerance to maximum voltage ratings makes no sense.
 
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FvM said:
Applying tolerance to maximum voltage ratings makes no sense.
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Why wouldn't it? if +/- 20% then volts can vary to those values. Its important if cap drops to lower voltage than its fed.
 

The capacitance tolerance is defined as the range within which lies "the most probable" value, whereas its voltage rating is defined as "the maximum allowed" value.
 
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if +/- 20% then volts can vary to those values. Its important if cap drops to lower voltage than its fed.
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Not a matter of tolerance. Useful cap voltage range is always 0 to maximum rating (or +/- maximum rating in case of a non-polarized cap). A negative tolerance can't be applied, neither a positive, you need to keep the maximum ratings. But you can operate the capacitor with any voltage up to maximum rating.

Tolerances are specified related to rated (nominal) capacitance, they can be quite different depending on capacitor type.
 
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I was worried because I don't want the cap to explode when it suddenly drops to a rated tolerance voltage. But I guess its not an issue.
 

I'm not sure what your working on but do you actually need a complete discharge of the capacitors.
In the case of a rail gun you may only need a few milliseconds discharge. If your capacitor takes say
100 milliseconds to fully charge and it only takes 10 milliseconds to launch the projectile. There will still be a good amount of charge left on the cap. Therefore the charging current and time to recharge is greatly reduced.
 
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I don't want the cap to explode when it suddenly drops to a rated tolerance voltage
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If at all, a cap can be damaged (or even "explode") if the discharge current is so high that the internal contacting is melting or evaporating. Or when exceeding the maximum rated voltage plus safety margin.
 
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