[Amps] Power supply design considerations

[Steve Katz]

> I am still working on the 4-1000A amplifier design and have decided to 
> separate the PS from the RF chassis.  I still don't have my HV 
> transformer but I am thinking that it will be too big to get into my 
> presently designed cabinet of 14" x 14" x 12" dimensions along with the 
> 4-1000A and all the plate tuning circuitry and filiment transformer.
> 
> I will be putting the power supply under the bench in a built in (wood) 
> cabinet that is already there.  The PS chassis/cabinet itself will be 
> made of aluminum but it will set on a shelf inside a closed door so I am 
> wondering about wheather I will have to wory about heat build up?  It 
> will be solid state diodes, capacitors and transformer. Do I need to put 
> in a fan in the side of the cabinet?
> 
> 
> ::You undoubtedly will, unless the cabinet's in a very cool
> air-conditioned room at all times.  You left out "bleeder resistors" from
> your parts list (above), and that's where most of the heat actually comes
> from.  For a 4kV power supply to bleed down to <40V inside of 10-15
> seconds (my normal criteria for discharging HV power supplies), your
> bleeders will be dissipating over 100W.  My own 4-1000A HV PS uses 80K of
> total bleeder resistance and dissipates 200W.  Without a cooling fan in
> the PSU, those resistors would likely burn up or unsolder themselves.....
> -WB2WIK/6
> 
> 
> The second item I am asking for design help on is the power cable to the 
> RF chassis.  This will run about 6 feet from the under desk cabinet to 
> the top of the desk through a hole in the bench.  It will be near my 
> knees so I dont want it to arc (5 Kv) to any part of my body.....#8-)  
> What should I use for transmission cable?  What is a source for such
> cable?
> 
> :: I use 20kV test prod cable, #18ga stranded conductor with silicone
> rubber insulation, readily available from many sources.  Mine is made by
> Gore, but lots of people make this stuff.  I use multiple, separate return
> and ground cables, but many feel more secure if the HV lead itself is
> shielded (not a bad idea), so you can slip the braid from some RG58 or
> RG59 cable over the HV test prod cable and use shielded, grounding
> connectors on each end if it makes you feel better.  (Frankly, it doesn't
> make me feel any better, at all, and I use ordinary 7kV Millen HV
> connectors with separate ground cabling.) -WB2WIK/6
> 
> 
> 
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