[Elecraft] KPA1500 Cooling

[W2xj]

glycol and anti freeze. 

Sent from my iPad

> On Jul 23, 2020, at 4:49 PM, N2TK via Elecraft <elecraft at mailman.qth.net> wrote:
> 
> Hi Paul,
> I can't remember what we used to use for closed loop cooling. I don't think we used distilled water because it's resistance would increase over time from picking up ions from the metal. In our case it was cooling loops in a copper 37" electrode. I thought it was some kind of antifreeze or maybe an oil? And also isn't distilled water quite reactive?
> To many bourbons ago 😊
> N2TK, Tony
> 
> 
> -----Original Message-----
> From: elecraft-bounces at mailman.qth.net <elecraft-bounces at mailman.qth.net> On Behalf Of Paul Christensen
> Sent: Thursday, July 23, 2020 3:54 PM
> To: elecraft at mailman.qth.net
> Subject: [Elecraft] KPA1500 Cooling
> 
>> "Until it leaks on the LDMOS devices."
> 
> Pure water is an insulator.  Leakage becomes a problem when water becomes contaminated with conductive particles.  This rarely occurs in closed loop systems that use distilled water when non-contaminating hoses, fittings, and heat exchangers are used.  My 2KW LDMOS amp uses water cooling in such a
> closed system.     
> 
> My main amplifier at home is an Alpha PA-70V.  The amp uses an openly-cooled vapor-phase system.  A pint of distilled water separates 4KV of plate voltage and chassis ground.  Water is in direct contact with the plate. In time, air particles do contaminate the water (usually in the form of algae) and the system must be purged and refilled at annual intervals.  If leakage exceeds a predetermined amount, the amp faults and shuts down.  
> 
> Paul, W9AC      
> 
> 
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