Re: DRSSTC thoughts...

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

Original poster: "Jim Lux" <jimlux-at-earthlink-dot-net> 

 > I don't know who started the DI water is a good thing years ago but I do
 > wish they would go away.

The ARRL Amateur Radio Handbook, probably.  Either there, or in some other
ARRL book, there's a whole discussion of watercooling (retrofit) a glass
envelope RF power tube, probably at 3kV anode voltage.  The original person
probably used distilled water, and somewhere along the line, I'd guess that
the wording got changed to DI (hey, it's a better insulator.. it must be
better, right?)

While ARRL does have lots of practical data, the accuracy and vetting of
little technical details (like DI vs other water) is probably not what one
would expect.  I had some back and forth with the editors about an article
published in QST for a 700V plate supply to replace a venerable tube based
supply and the picture showed a DMM connected with the tiny Radio Shack
style clipleads tangled with the power cord, etc.  And, there were some
component rating and design safety issues.   Not that it can't be done
safely, it's just that the pictures shouldn't encourage bad practices.  The
author of the article responded directly to me, and made some assertions
which, while I hesitate to call them outright lies, would be tough to
validate (i.e. he claimed the wires in the photo were HV clipleads... which
made me wonder if he had ever seen real HV wire).  I can fairly confidently
assert that the author had no HV design experience (where HV is defined as
 >100V) based on his component selection and layout.  What makes it worse is
that he's selling kits.


  I run into this issue almost every day in tech
 > support. DI may have it's place but not when your metal is going to be
eaten
 > away in critical places!
 > Mike
 >
 > ----- Original Message -----
 > From: "Tesla list" <tesla-at-pupman-dot-com>
 > To: <tesla-at-pupman-dot-com>
 > Sent: Wednesday, September 29, 2004 12:20 AM
 > Subject: Re: DRSSTC thoughts...
 >
 >
 >  > Original poster: Terry Fritz <teslalist-at-twfpowerelectronics-dot-com>
 >  >
 >  > Hi,
 >  >
 >  > "DI" water trends to "tear up" things...  We have a 60KW generator here
 >  > that can waist 30kW into the dirty cooling water as a pure resistive
 >  > VI...   Water cooling "can be" like 100X better!!!  But be very careful
of
 >  > having voltages across that water barrier...  We have giant IGBTs with
 >  > water directly on their backs, but thermal studies suggest we need
copper
 >  > heat spreaders instead for max dissipation...  Big tubing lengths are
 >  > legendary for fighting this... but that gets silly after a point....
 >  >
 >  > Cheers,
 >  >
 >  >          Terry
 >  >
 >  >
 >  >
 >  > At 10:05 PM 9/28/2004, you wrote:
 >  > >Hi Terry, Steve and everyone,
 >  > >    About the cooling issues, especially the die's, and whole devices,
I
 > like
 >  > >water cooling. Distilled water of course and non-conductive hose, ~1
foot
 >  > >per kV in length and then some safety factor. At work we routinely use
it
 >  > >cooling the big triodes of induction heaters of 600 kW output class
and
 > also
 >  > >for the "hockey puck" large SCR's controlling the 480 volt 3 phase to
the
 >  > >transformer primary. Leakage to ground is not a problem with good
water,
 > msnip....
 >
 >