Will the voltage required to kill one capacitor also kill an array or identical capacitors?

Question

Suppose you have a simple circuit with a voltage source and a capacitor.

The voltage difference is _just_ high enough that the capacitor will arc and fail.

If you had an identical circuit but with 2 capacitors in parallel, (or any array of capacitors in parallel, could be 1,000,000) would this second circuit also fail?

Please do not answer if you are not positive in your answer. That is, I do not want to hear "the voltage across each is the same. so it will always fail." I'm aware of that. If that's the case, what exactly would happen with the array? Would each capacitor fail?

Thank you!

Answer 1

If your question is academic, involving idealized components, then "Yes, all capacitors would fail simultaneously.

However, if you are talking about the real world, then flipping the switch on a highly capacitive load would result in a current surge, which could result in:

1. The switch contacts melting.

2. The wiring melting.

3. The power supply failing.

4. One or both capacitors failing.

5. Any combination, including all, of the above.

So much depends on the ratings of the components, the actual tolerances, variances and safety margins, how they are wired, what the ambient temperature is, and a host of other factors that aren't being addressed here.

Answer 2

Yeah the voltage would be the same but that would really only matter if you exceeded the voltage rating of the caps. Putting caps in parallel your effectively increasing the surface area of the plates and increasing the total capacitance of the circuit. So you will be able to store more charge. The circuit should not fail unless you overcharge the caps in the circuit.

Answer 3

yes, if you exceed the voltage rating of a cap, it may fail.

But no two caps are identical. They may be rated at, say, 400 volts, but one may fail at 420 volts, another at 450 volts, another at 405 volts. Temperature is also a factor.

So if you have 10 caps in parallel and you slowly increase the voltage above 400 volts, there will be one that fails first, say at 420 volts. It will short out the supply, and make a lot of smoke, as it discharges all the rest of the caps.  If you remove the dead one and repeat the experiment with the remaining 9, you may find that you have to go above 420 volts to get the next one to blow up, or you may find that you damaged one of the others and it blows up at a lower voltage.

Remember that voltage over the rating is detrimental to the health of a cap, and you may cause partial damage that will make it more liable to fail in the future.

Perhaps your question is theoretical, and I'm to assume they all have the same breakdown voltage? But that's not possible, even theoretically.

Even one cap can be considered a bunch of smaller caps in parallel, thousands or millions if you want. Each of those smaller caps has a breakdown voltage, and what happens as you raise the voltage, is that one of the sub-caps breaks down, and the discharge of the rest of the cap through this small area causes the smoke and flames.

Or are you asking if the breakdown voltage changes as you put more caps in parallel? the answer to this is NO, why would it? Each cap sees the voltage applied to it, and breaks down if that voltage is above it's rating.