Re: Cap - Puncture Voltage
Sent: Wednesday, December 03, 1997 10:25 AM
Subject: Re: Cap - Puncture Voltage
In a message dated 97-12-03 04:01:20 EST, you write:
<< AC and especially Tesla Coil use. I have found a local supplier that has
30mil 4' x 8' sheets at $13/sheet. What is a "real" assumption I can use
for puncture voltage? What do you guys use? I know need to over-engineer
the cap, but going overboard can really screw up the numbers and my
wallet. It's been stated that a .090 thickness (from a few thin layers
or just one thick one) can withstand 15,000V. If this is true, then were
talking 167V/mil as a puncture voltage. I would assume this has been
derated for AC use? Anyone have a good guess at what I should use for a
puncture voltage on a per mil basis?
Based on my experience, having built three rolled poly caps and blown two of
them - I think three layers of .030 poly will safely operate in a Tesla tank
circuit with a 12 kv transformer for power. I don't think it will be bullit
proof at 15 kv. For 15 kv, I think you will need four layers of .030 poly.
The two caps that failed utilized only one layer of .062 poly and failed at
12 kv. The one cap remaining uses two layers of .062 poly. Your selection
of multiple layers of .030 is good but I would not be comfortable with only
.090 mils at 15 kv. Let's see what others have to say.