Re: Arctronics capacitors

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

Original poster: Terry Fritz <teslalist-at-twfpowerelectronics-dot-com>

Hi,

At 12:59 AM 2/23/2004, you wrote:
>Yes it is the model 37667 35 kvdc and 30 nF. The cap didnt work for 2 days
>before explosion. I ran my coil for maybe second or two ( just turned variac
>to max) and the top of capacitor ( where the sticker is ) just ripped and
>flyed around the room messing evrything with oil and oil did also spring
>from capacitor! So i so i was sad, after i cleaned the mess and taked the
>cap out and leave it dry it didnot have any visual damage. After it dried i
>tried again, and agin it worked for a few times and then blew forever. This
>cap is made from 8 caps, 4 strings in series, every string has 2 caps in
>parallel. Every cap is rated 8750 V and 60 nF.

Interesting!!  I assume these are foil/poly wrap types with heavy 
leads.  Maxwell probably makes the smaller sections and then strings them 
up for different caps values just like we do with MMCs.

>I still have some caps from
>inside. Intresting thing when i tried one cap from inside it worked ok so i
>disasembled it it was black inside and full of holes like swiss chese.

It had many small breakdwons from being way overvoltage.  Possibly the 
failure of another section of the cap put all the voltage stress into the 
remaining good sections.  The "machine gunned" dielectric is typical if the 
cap is run at high voltage and it is breaking down all the time.  They can 
take a lot of holes!!  But they will go bad eventually.  Very interesting 
that the sections in these caps appear to be of the self healing type!  If 
you can send pictures, it would be cool to see what they are like inside.

I would not normally think the holes would be part of the wearout.  I 
thought these were former laser caps.  Pulse caps do suffer from mechanical 
damage after time.  If the dielectrics have multicolored rainbow patterns 
on them that would indicate ionization damage.  Unlike MMCs, one can't take 
out one cap and tear it apart to judge the condition of the rest of the MMC.

>So my
>opinion is that maywells 37667 are better than Cornell Doublier because they
>are also self healing, more practic and so.

I have some 37667 types for another use where I need super high currents 
(10,000's of amps)  Typical MMCs won't do that.  The Maxwells also have 
super low inductance.

>The only problem was in my
>Maxwell that the seller sucked all life from him and sold it to me. Does
>anybody on the list wants to sell a maxwell HV cap any model at reasonable
>price? Maybe somthing like Terry Blakes capacitor?

Mine are from TSR too....  Hard to say if they are good or bad...  They 
measure and basically test ok.  But why not use a standard MMC instead?

http://www.tb3-dot-com/tesla/capacitors/capacitors.html

I think the MMC would be cheaper than even the used Maxwell caps.

Cheers,

         Terry


>----- Original Message -----
>From: "Tesla list" <tesla-at-pupman-dot-com>
>To: <tesla-at-pupman-dot-com>
>Sent: Monday, February 23, 2004 12:42 AM
>Subject: Re: Arctronics capacitors
>
>
> > Original poster: Christoph Bohr <cb-at-luebke-lands.de>
> >
> >  > Original poster: Kreso Bukvic <kreso.bukvic-at-kc.htnet.hr>
> >  >
> >  > My previous maxwell exploded. For a few minutes after exploded, he ...
> >  > died! What isa the maximum AC voltage for this cap? I used 10 kV 100 mA
>nst
> >  > resonant?
> >
> > Hello Kreso.
> >
> > Very sad to hear about your rmishap with the maxwell cap. Did the cap heat
>up
> > before or did it explode without warning? What exactly happened? Did the
>case
> > break open or did it really explode with burning oil and pieces flying
> > around? Was this the type of cap Alltronics sells ( 37667 )?
> > I am very interested in any experiences with this cap as it is the only
>real
> > HV cap type I own.
> >
> > best regards
> >
> > Christoph Bohr
> >
> >