Re: [TCML] Capacitors for MMC

[Gary Lau <glau1024@xxxxxxxxx>]

Shawn, I think the graphs you're referring to apply only to applications
requiring the capacitors to be operational 24/7 and still have reasonable
industrial life expectancies.  The truth is, with the way we use MMC caps,
they won't be able to run constantly for years without failure.  If we
required such long lifetimes, we'd have to operate at much lower voltages
per cap, which would require much longer strings of caps and much greater
expense.

However, the total lifetime run time of a capacitor in a hobbyist-grade coil
is probably not more than a couple of hours, and acknowledging that allows
us to build a cap for a  fraction of what one built to run constantly for
years would cost.  Yes we're violating the specs, but the same is true for
any of the MMC caps, not just these.

Regards, Gary Lau
MA, USA

On Sun, Dec 12, 2010 at 10:04 PM, Shaun Epp <scepp@xxxxxxx> wrote:

> I don't think those capacitor will work for Tesla coils.  If you look at
> the curves of applied voltage vs frequency on the web site, these capacitors
> roll off at much lower frequencies than we work with.  In other words we
> couldn't apply a high voltage to them at primary/secondary frequencies.
>
> See
> http://www.kemet.com/kemet/web/homepage/kechome.nsf/file/PHE450%20Series/$file/F3294_PHE450.pdf
>
> Shaun Epp
>
>
>
> Date: Sat, 11 Dec 2010 10:10:46 -0800
>> From: "Bob Deuel" <k2glo@xxxxxxxxxxxxxx>
>> Subject: Re: [TCML] Capacitors for MMC
>> To: "Tesla Coil Mailing List" <tesla@xxxxxxxxxx>
>> Message-ID: <591A78BF7702437CA88E9B2C888E3D99@bdeuel64>
>> Content-Type: text/plain; format=flowed; charset="iso-8859-1";
>> reply-type=response
>>
>> Thank you Bert. That is exactly the information I was looking for.
>> Bob
>>
>> ----- Original Message ----- From: "Bert Hickman" <
>> bert.hickman@xxxxxxxxxx>
>> To: "Tesla Coil Mailing List" <tesla@xxxxxxxxxx>
>> Sent: Friday, December 10, 2010 10:56 PM
>> Subject: Re: [TCML] Capacitors for MMC
>>
>>
>> Hi Bob,
>>>
>>> Per the following site, the PHE431 series is an obsolete polypropylene
>>> film cap that has been superseded by the Evox Rifa PHE450 series. They
>>> are
>>> indeed constructed with a polypropylene dielectric with double metalized
>>> polyester film as electrodes (i.e., the polyester is used as a mechanical
>>> structure but NOT actively used as a dielectric in the capacitor). The
>>> series is rated for high frequency applications with high current stress.
>>> Sounds like a potential TC MMC app to me... :^).
>>>
>>> http://www.pikpower.com/new site/evoxrifa_b/evoxrifa_crossref.html
>>>
>>> The specs for the PHE450 series can be found here:
>>>
>>>
>>> http://www.kemet.com/kemet/web/homepage/kechome.nsf/file/PHE450%20Series/$file/F3294_PHE450.pdf
>>>
>>> Good luck,
>>>
>>> Bert
>>> --
>>> ********************************************************************
>>> We specialize in UNIQUE items: coins shrunk by ultra-strong magnetic
>>> fields, Captured Lightning Lichtenberg figure sculptures, and scarce
>>> technical Books. Please visit us at http://www.capturedlightning.com
>>> ********************************************************************
>>>
>>> Bob Deuel wrote:
>>>
>>>> I picked up some 100n (0.1uf) @ 1000v and 33n (0.033uf) @ 1500v
>>>> "RIFA 431" series capacitors at a swap meet that I would like to use
>>>> for a MMC. I assume that they are film capacitors. They have light
>>>> blue 1.2"x0.9"x 0.55" rectangular plastic cases with radial leads. I
>>>> have tried to find catalog reference data for the RIFA 431 series but
>>>> I am not having any luck. I can find other series of Evox RIFA (now
>>>> Kerment) capacitors but not the "431". My main question is if anyone
>>>> knows if they are pulse rated and the type of film dielectric they
>>>> have. Also has anyone sucessfully used them in a MMC? Thanks in
>>>> advance, Bob _______________________________________________ Tesla
>>>> mailing list Tesla@xxxxxxxxxx
>>>> http://www.pupman.com/mailman/listinfo/tesla
>>>>
>>>
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