Re: MMC

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "brian by way of Terry Fritz <twftesla-at-qwest-dot-net>" <ka1bbg1-at-mcttelecom-dot-com>

ha. it would be like buying a sears handtool! guarantee sounds awesome to
me! brian F.

----- Original Message -----
From: "Tesla list" <tesla-at-pupman-dot-com>
To: <tesla-at-pupman-dot-com>
Sent: Tuesday, May 29, 2001 2:40 PM
Subject: Re: MMC


> Original poster: "Terry Fritz" <twftesla-at-qwest-dot-net>
>
> Hi Chris,
>
> At 05:28 AM 5/29/2001 +0000, you wrote:
> snip...
>
> >The Group is (within the next few
> >weeks) going to guarentee it's caps. This will be a retroactive guarentee
to
> >everyone who has already bought a Group MMC cap and also for future
sales.
> >It will basically be something along the lines of "If you buy your MMC
caps
> >from the Group, hook them up in a properly designed manner and run them
> >within reasonable limits (their design specs) and they fail, we'll send
ya
> >new ones in exchange for the old ones (we autopsy the old ones to see how
> >you killed it).
> >
> >What do you guys think of this? Ideas? Thoughts?
> >
> >
> >Duck
> >Geek-1
> >
>
> Since the caps have such high voltage and current ratings, failures should
> be very rare.  Examining the ones that do fail is very valuable!  They are
> easy to autopsy and a great way to study how they work in our very rough
> service.  It also gives the cap manufacturers a special look into how poly
> caps behave that their competitors don't have ;-)
>
> Some caps are going to die from "user error".  I found that sending along
a
> sheet with the following tips really helped stop most common mistakes.
> Well worth the $0.05 to send it along with all orders.
>
> I would especially watch #s 2, 3, and 4.1
>
> Cheers,
>
> Terry
>
>
> --------------------------------
> Here are the essential tips in building MMCs:
>
> 1. Always make the strings individually selectable so you can get many
> different values of capacitance.
>
> 2. Leave a small (~1/8")air space in between the caps in a string for
> air flow and to leave room if one fails.
>
> 3. Be sure to leave a good distance (~1" or more) between the strings
> so if some are not used, that active strings will not arc to inactive
strings.
>
> 4. Put 1/2W 10Meg ohm (or some close value) resistors across each cap for
> safety and balancing.*
>
> 4.1 Do not place the resistors directly against the capacitors! The thin
> capacitor shell may not provide good insulation. The capacitors need a
good
> space between them and other objects to insure they will not arc over. I
> would recommend about 1/4 inch clearance between the capacitor cases and
> other things.
>
> 5. Be sure the resister leads are actually wrapped around the cap leads
> so they will stay in place if the solder gets hot or the solder connection
> was not sound.*
>
> 6. Remember that the whole cap is at very high voltage so it needs to be
> mounted away from metal and in a safe location.
>
> 7. Perfboard, like DigiKey# V1011-ND, makes mounting the caps really easy.
>
> 7.1 Be careful when bending the leads not to damage the connections inside
> the capacitor. Tubular style caps can especially have fragile lead
connections.
>
> 8. Do not connect the caps between strings together even though they are
> at the same potential. This defeats the cap's self healing and value
> selection features.
>
> 9. Even though the cap leads seem small, use heavy primary wiring and try
> to use brass or copper connections as with any Tesla cap. Bringing the
ends
> of each string to 1/4" brass bolts works well.
>
> 10. Remember that even a small EMMC cap can be just as dangerous as many
> big oil filled caps... The resistors go a very long way in making them
safer
> but don't get careless.
>
> * People have gotten shocked by not doing these.
> -------------------------------------
>
>
>
>