Re: Swap a 1000uf 10V for a 1500uf 16V
They are called electrolytic because the chemical & electrical processes that go on inside are electrolysis. When the cap is manufactured the oxide layer may be created by whatever means but once it's in use it works similar to electroplating.
[Although what gets plated is an oxide and not a pure metal or alloy.]
To understand lytic caps you have to stop thinking in terms of voltage on the cap and think in terms of current through the cap.
In terms of current through the cap, the cap is a resistor with a value based on the thickness of the oxide layer.
~~
One half cycle of the alternating ripple current thins the layer. - Reverse current half.
[Same with negative swing of signal currents.]
-
Time also thins the layer by the oxide's natural chemical interaction with the electrolyte. This is what shelf life is based on and why old caps need 'reformed'.
The leakage current from applied DC thickens the layer.
- As the layer thickens the resistance goes up and leakage current goes down until an equilibrium point where the electrolyte can't provide any more oxide. [A higher applied voltage can 'drive' more oxide out of the electrolyte creating a thicker layer.]
Ripple [and time] thins the layer causing leakage to go up.
The leakage current then rebuilds the layer causing leakage to go back down.
- This is why lytics used to be called 'self healing' caps.
*The amount of leakage current is dependent on the applied voltage.
*The 'rebuilding' will only occur up to a thickness consistent with the applied voltage.
~~
Now, if you apply too much voltage for the existing thickness of the layer you can overwhelm the rebuilding process and end up with what amounts to arching from plate to plate [right through the oxide layer] and that will damage the layer beyond repair. In that case the leakage will go up and continue going up until the cap shorts or opens or is so far out of spec it is useless in the circuit.
~~
I tried making some animated videos of what goes on inside caps a while ago but animation isn't exactly my forte. I suck at it.
.
They are called electrolytic because the chemical & electrical processes that go on inside are electrolysis. When the cap is manufactured the oxide layer may be created by whatever means but once it's in use it works similar to electroplating.
[Although what gets plated is an oxide and not a pure metal or alloy.]
To understand lytic caps you have to stop thinking in terms of voltage on the cap and think in terms of current through the cap.
In terms of current through the cap, the cap is a resistor with a value based on the thickness of the oxide layer.
~~
One half cycle of the alternating ripple current thins the layer. - Reverse current half.
[Same with negative swing of signal currents.]
-
Time also thins the layer by the oxide's natural chemical interaction with the electrolyte. This is what shelf life is based on and why old caps need 'reformed'.
The leakage current from applied DC thickens the layer.
- As the layer thickens the resistance goes up and leakage current goes down until an equilibrium point where the electrolyte can't provide any more oxide. [A higher applied voltage can 'drive' more oxide out of the electrolyte creating a thicker layer.]
Ripple [and time] thins the layer causing leakage to go up.
The leakage current then rebuilds the layer causing leakage to go back down.
- This is why lytics used to be called 'self healing' caps.
*The amount of leakage current is dependent on the applied voltage.
*The 'rebuilding' will only occur up to a thickness consistent with the applied voltage.
~~
Now, if you apply too much voltage for the existing thickness of the layer you can overwhelm the rebuilding process and end up with what amounts to arching from plate to plate [right through the oxide layer] and that will damage the layer beyond repair. In that case the leakage will go up and continue going up until the cap shorts or opens or is so far out of spec it is useless in the circuit.
~~
I tried making some animated videos of what goes on inside caps a while ago but animation isn't exactly my forte. I suck at it.
.
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