[TenTec] paralleling several dc supplies to increase I capab

[John - G3JAG]

If you look into a TT 9420 100A supply (as I have had to do on numerous
occasions - until I found the dry joint) you will see that it is four
identical 25 amp supplies... These have to be set to within 0.1V of
each other (and mine stay that way once set). If they get out of
balance the supply quits.

The 20A Omni-V supply is taken from all four 25A rails, but uses
steering diodes to share the load and isolate the individual rails from
a fault on any one.

Generously rated and heat sunk steering diodes are part only of the
answer to paralleling things - if you must. Personally I'd rather have
a set of separate 25-30A analogue supplies than one mega-amp unit that
needs a fork lift to move it. The switch-on surge is another matter.
Treble the fire insurance and have a bigger supply cable put in by the
power company. Fit 6 inch nails in the fuse box. Buy some (dry)
extinguishers.

BTW I guess the Astron is very similar to some Far Eastern switch mode
supplies over here (same box, different label ??) I tried one and it
was like a sub-woofer. When I spoke or hit the key, there was a
seriously LOUD AC buzz. It was completely incurable, so I took it
back. The replacement - with a different label/box - just has a noisy
fan. I got so tired of it that I finally found the energy to haul out
the 9420 for a more serious investigation. Amazing what strange
symptoms can result from just one bad joint on a plug/socket
connector.
 
Analogue with over-current/over-volt protection, and no fans, is
the way to go. If it weighs less than 20 pounds its probably not big
enough.
 
73 John
 
On 30-Jul-99 Carl Hyde wrote:
> 
> I have one or two suggestions.  Increase your fire
> insurance policy to the replacement value of your home
> then go seek professional electrical and psychological
> help.  Power supplies are not batteries.  You run the
> risk of unbalanced loads in each supply, harmonic
> coupling from transformer quadrature, and without a
> sophisticated current and voltage regulation system
> you will never be able to balance the load to each
> supply.  Sell some of them and buy a sufficient power
> supply for your amp. I don't mean to be harsh on this
> but it is a bad and dangerous idea. 
> 
> --- zeitler@ibm.net wrote:
>> 
>> First of all let me start off by saying that I have
>> added both boatanchors
>> groups to this e-mail because the wealth of
>> knowledge on these two groups is
>> unparalleled. Please forgive me for having the nerve
>> (or foolheadedness) to
>> ask a question regarding solid state stuff on the BA
>> list.
>> 
>> Here is the scenario: Eventually I would like to add
>> a solid state HF amp to
>> the ham shack. I have numerous Ten Tec and Astron
>> supplies. When paralled
>> they should provide well over 160 amps btwn the 8
>> supplies. I have two sides
>> of the 240 in the shack so 4 supplies would be on
>> one and the other four
>> would be on the other so not all of them are on just
>> one 120 volt line.
>> 
>> What is the best method of paralleling and combining
>> the outputs of these
>> supplies so they are all getting the same current
>> draw? I assume I need to
>> ensure that the voltage accross the string of them
>> is equalized.
>> 
>> Ideas?
>> 
>> Lane
>> Ku7i
>> 
>> 
>> --
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> 
> ===
> Carl S.HYDE
> W2CSH
> 
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> 
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E-Mail: John - G3JAG <patents@dx0man.prestel.co.uk>
Date: 30-Jul-99
Time: 08:53:58

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