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Re: [TCML] Voltage - Gap



On 2/3/12 9:27 PM, Carl Noggle wrote:
True. Such things often have interesting power dependencies. The life if
an incandescent light bulb is inversely proportional to the thirteenth
power of the applied voltage. Bandsaw blade wear, the seventh power of
the excess cutting speed. Wonder what the dependency is for cap voltage,
rep rate, etc.?



life is in cycles, for the most part, because the "wear out mechanism" is the stress on the dielectric/plate system. There are also some factors that are temperature related (whether external environment or due to internal dissipation)

Most all is revealed at
 http://home.earthlink.net/~jimlux/hv/caplife.htm
 with some examples...

Lx = Lref * (Qref/Qx)^1.6 * (Vref/Vx)^7.5

Q = sqrt( 1 + 1 /( 2 /pi*ln(VR))^2)

There are some differences in the life prediction equations depending on the actual dielectric being used and the construction. So what works for a foil/poly as used in the Maxwell plastic cased (white brick) capacitors won't necessarily be valid for paper/castor oil (big metal can pulse caps) or the PP film caps used in a MMC.

Somewhere back in the archives (really) there was a list of the "age derating" exponents for some of the other dielectrics.
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