Re: Cooling MOFSETS and IGBT's.

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

Original poster: "by way of Terry Fritz <twftesla-at-uswest-dot-net>" <Tesla729-at-cs-dot-com>

In a message dated 3/19/01 6:53:45 PM Central Standard Time, tesla-at-pupman-dot-com 
writes: 


>
> > Distilled water as the coolant would work quite nicely, and hold off 
> > the 30 kV. 
> > 
> > or, run entire water cooling rig "floated" at the HV. 
>
> But will it remain distilled in contact with various voltages and 
> metals? I don't think I'd have water anywhere near HV of any sort and 
> the thought of dripping condensation doesn't appeal either if for no 
> other reason than corrosive effects. 
>
> Regards, 
> malcolm 
>
>


Hi all, 

Malcom's right! And BTW, I tried to measure the resistance of distilled 
water vs. tap water one time years ago and although the tap water obvi- 
ously had much more resistance that the plain tap water, the distilled 
water did indeed have some conductance. If my memory serves me cor- 
rectly, I think by just placing the ends of the multimeter probes about 
an inch into a drinking glass full of each kind of water, the tap water read 
~ 20 kOhms and the distilled water ran around 400 kOhms. I don't think 
this would be near enough resistance to hold off any serious high voltage, 
but would allow for some current flow, which in affect, would short it out. 
Example: 10 kV thru 400 kOhms = 25 mA of current leakage or 250 watts. 
And at 30 kV, there would be over 2000 watts of power wasted this way in 
the form of heat, assuming 400 ks of resistance! And I'm sure there would 
be more surface area of exposed oppositely charged HV conductors in 
this setup than with the two slender multimeter probes. 

David Rieben