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Re: [TCML] 833A vacuum tube filament current



Good info Dave.

For highly-stressed metalized polypropylene pulse capacitors, the exponent can be _as high as 15!_ This is also why the specified maximum percent voltage reversal may only be 10 or 20%. DON'T overvolt your polypropylene pulse caps - especially those that do not use self-healing technology.

Bert

David Rieben wrote:
(Did you know that the life of an incandescent bulb is inversely proportional to the thirteenth power of the applied voltage? A sobering thought.)

Interesting. That would explain why 130 volt rated incandescent bulbs are more expensive and rated to have a considerably longer operational life than their 120 volt rated counterparts: 130/120 = 1.083;
1.083^13 = 2.83X greater operational life expectancy.

Capacitors have a similar applied voltage vs. operational life relationship as well, especially once they are overvolted beyond their nameplate rating, even though the power factor gradient is typically not that sharp and ambient temperature environment also plays a major role in capacitor longevity.

http://www.illinoiscapacitor.com/tech-center/life-calculators.aspx

David Rieben


----- Original Message ----- From: "Carl Noggle" <cn8@xxxxxxx>
To: "Tesla Coil Mailing List" <tesla@xxxxxxxxxx>
Sent: Sunday, February 18, 2018 9:21 AM
Subject: Re: [TCML] 833A vacuum tube filament current


Limiting the inrush current to anything that heats up seems like a good idea. Most damage to paleolithic (incandescent) light bulbs occurs during the current inrush period. (Did you know that the life of an incandescent bulb is inversely proportional to the thirteenth power of the applied voltage? A sobering thought.) Besides, if anyone knows what they are doing, it's Machlett.

How about a big varistor?

--- Carl



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