#homecmos IRC log for Monday, 2012-11-12

--- Mon Nov 12 201200:00
Syncbah still unsure what is the easiest and cost effective way to make vacuum chambers19:42
Syncfavoring a brazed Al construction now19:43
berndjyou building your own vacuum chamber?22:03
Syncyeah still on it22:04
SyncI need several too22:04
berndjpumps?22:04
SyncI have most types of pumps that are commonly used22:05
berndjwhat motivates against stainless steel?22:06
Syncthe cost22:06
berndjthey cost the same at my local scrap yard22:07
SyncI currently cannot weld Al which is annoying so I have to braze or oxyweld it22:07
Syncyes but I'm not going to use scrap metal22:07
berndjfair enough :)22:07
Sync(only because my local scrapyard does not have stainless in sizes I want)22:08
berndjcan you TIG at all, or just not do it to aluminium, or not at all?22:09
SyncI do have a TIG welder22:09
berndjcheap one / fancy one?22:10
Syncit is a chinese one but it works reasonably well22:10
Syncbut I almost finished my ac tig inverter22:10
berndjsame here, but mine can only output DC, so probably can't do aluminium22:11
SyncI just need some better mosfets in the bridge to keep the losses low22:11
Syncyou can do Al with a regular dc tig welder22:11
berndji've been back-of-the-enveloping a diy welder too22:11
berndji can't get it to work out cheaper than buying one :(22:11
Syncyou just have to use DCEP and preferrably Ar/He mix22:11
berndjoh right, the DCEP trick22:12
Syncoh it was cheaper for me than buying one22:12
berndjwith a giant fat tungsten electrode so you can just barely weld the thinnest sheet!22:12
berndjso, out with it then, what mosfets?22:12
berndjbeefiest i've been able to find so far are IRF*2907*22:13
berndj* cost-effectively-beefiest22:13
Syncthe 2907 have too low Vdss to have a good safety margin22:14
SyncI have FDH055N15A22:14
berndji'm tempted to build an H bridge to chop up the DC output from my welder, but i don't know the welder well enough to know if it'll get angry about it22:14
berndjwhat open circuit voltage are you working at?22:14
Syncactually, I have not measured it22:15
Syncbut it is around 60V iirc22:15
berndjmine hovers at about 75V22:15
Syncthen your fets will be no good22:15
berndjdunno what limits it22:15
berndjyeah, 2907 is 75V i see now22:16
SyncI also have some IPW65R037C6 for the primary converter22:16
Syncthe most costly semi in the thing is the SiC diode in the PFC22:18
SyncI currently combat some strange transients that kill my primary fets22:20
berndjoh and what's your capacitor bank like?22:24
berndjthe caps i can find don't really seem up to the ripple current required22:25
SyncI don't have many caps in there22:35
--- Tue Nov 13 201200:00

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