Capacitor voltage tolorance without a label

Thread Starter

l0vot

Joined Apr 29, 2013
107
I have come across an Aerovox mica condenser, the label that was printed on the side is too damaged to read, my LC meter claims it's a 2.727nF cap, which is quite small for a cap that weighs a little more than a pound. Would there be any way to find the voltage tolerance of the cap without destroying it?
 

MrChips

Joined Oct 2, 2009
30,707
No one labels a capacitor as 2.727nF.
What exactly does it say on the package? A photo would help.
A lot of capacitors are 20% tolerance.
Voltage? Give yourself 50% margin, i.e. use a 50V rated capacitor in a 30V circuit.
 

MaxHeadRoom

Joined Jul 18, 2013
28,617
If small value and weighs > 1Lb then it could be a 20kv rating as used in TX applications etc.
In any event it would be special purpose.
Max.
 

ian field

Joined Oct 27, 2012
6,536
I have come across an Aerovox mica condenser, the label that was printed on the side is too damaged to read, my LC meter claims it's a 2.727nF cap, which is quite small for a cap that weighs a little more than a pound. Would there be any way to find the voltage tolerance of the cap without destroying it?
If a 2.7nF capacitor weighs that much - I'm kinda thinking you'll be putting yourself in danger before you get anywhere near the capacitor's breakdown voltage.
 

Thread Starter

l0vot

Joined Apr 29, 2013
107
Thank you MaxHeadRoom and ian field, that should mean it would make a good cap to use for high voltage, high power RF applications. I still would like to know if there is a way to find the max voltage of a cap without breaking it, but that probably isn't a thing that can be done cheaply, if at all.
 

crutschow

Joined Mar 14, 2008
34,281
Thank you MaxHeadRoom and ian field, that should mean it would make a good cap to use for high voltage, high power RF applications. I still would like to know if there is a way to find the max voltage of a cap without breaking it, but that probably isn't a thing that can be done cheaply, if at all.
Nope. It's rather like testing a fuse to determine its current rating. It's a destructive test.
 

ian field

Joined Oct 27, 2012
6,536
Thank you MaxHeadRoom and ian field, that should mean it would make a good cap to use for high voltage, high power RF applications. I still would like to know if there is a way to find the max voltage of a cap without breaking it, but that probably isn't a thing that can be done cheaply, if at all.
Leakage would rise just before actual breakdown - but not in any sense anything like an electrolytic. The leakage would rise a very tiny amount with an extremely narrow margin for detection.

Mica capacitors were always the first choice in most RF applications, but there's no such thing as a perfect capacitor - it will get hot at RF as you get near its limits.

This may be your best guide to how far you can stress it.
 
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