Re: DRSSTC thoughts...

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

Original poster: "Mike" <induction-at-comcast-dot-net> 

Hi Terry,
                  Oh Yes, "DI" Water is very un-good. In fact, when we sell a
water cooled ceramic cap or "mushroom" cap, we put a sticker right on it
that DI water is NOT to be used or the warranty is void. DI water eats metal
and thus the thin barrier. Typically, a machine with these caps will start
leaking at the barrier in about 18 months as the metal has got so thin.
Steam distilled water is best and has no problems like DI water.
The typical tube generator does run just a bit over 50 percent out, so your
60 kW machine will usually have a 120 KVA  plate transformer. The solid
state machines are much better. In the 80 percent area and easier to cool on
exchanger demand. Because of the high currents and skin effect, most of that
is I/R losses. And yes, the water on the SCR's is indeed on the hot side but
as long as the water feed and drain manifolds are grounded to the frame on
the way in and out of the machine, any leakage stops there and does not go
external to the heater itself.
I don't know who started the DI water is a good thing years ago but I do
wish they would go away. 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....