[Amps] Series PC Power Supplies

[Jim Tonne]

Will:
If the supplies are in series wouldn't each be passing
the same number of amps?  What is there to "balance"?
What do you mean by "placing rectifiers across..." each
supply?
- Jim WB6BLD


----- Original Message ----- 
From: "Will Matney" <craxd1 at verizon.net>
To: <amps at contesting.com>
Sent: Thursday, June 01, 2006 3:07 PM
Subject: Re: [Amps] Series PC Power Supplies


> Another recommended practice is to place rectifiers across the + and - of 
> each supply to try and balance the load. If the load is not balanced 
> across each, one supply can be overburdened if just slightly off from the 
> others. The rectifiers need to be rated at the same current capability of 
> the total supply in a series connection. The low side supplies ground will 
> be the supply ground and the ground for the last rectifier in the string. 
> This is shown in several power supply books that mentions seriesing and 
> paralelling supplies for increased voltage or current. Generally though, 
> this practice of using several supplies is not really recommended because 
> of the balancing problems.
>
> Best,
>
> Will
>
>
> *********** REPLY SEPARATOR  ***********
>
> On 6/1/06 at 11:57 AM Joe Isabella wrote:
>
>>Two things...
>>
>>1. You can get a brand new 25A switching supply for $80-90 if you look
>>around.  I bought my Samlex 25A for $80.
>>
>>2. How did you series the supplies you have?  The "first" one will provide
>>your "ground" connection.  Take the red wires from that and connect them
>>to the black wires of the "second" supply.  Now take the red wires from
>>that one, and connect them to the black wires of the "third" supply, which
>>will provide the positive (15 VDC from the black wires of the "first"
>>supply to the red wires of the "third" supply, in this case) to your rig.
>>Make sure you tied the orange wires to each supply's red wires so they all
>>see "power good" line properly.  Make sure you have isolated the black
>>leads from chassis ground on the second & third supplies as as the article
>>says since they need to be floating (otherwise, the 5V from the first &
>>second supplies will be going straight to ground).  If you didn't isolate
>>them, you'll only see the 5V from the "third" supply...
>>
>>Joe, N3JI
>>
>>----- Original Message ----
>>From: aborg <a_borg at yahoo.com>
>>To: Amps Amps <amps at contesting.com>
>>Sent: Thursday, June 1, 2006 9:09:38 AM
>>Subject: [Amps] Series PC Power Supplies
>>
>>
>>Hello Amp'ers,
>>
>>Quick technical question. I'm embarrassed that I
>>can't figure this out, but not quite a super tech yet.
>>Here it is. I am attempting to series 3 pc pwr
>>supplies. I can't seemed figure why I'm only seeing 5+
>>volts. The link to the article is below. Here is an
>>excerpt from the article. "Our second means of
>>utilizing this low cost power is to connect the +5 VDC
>>outputs of three separate supplies together in series.
>>This will provide you with +15 VDC at 25 amps on up to
>>the maximum rating of the supplies you have acquired."
>>Can someone be kind enough to relieve from my
>>embarassment ?
>>
>>Thanks
>>
>>http://www.antennex.com/preview/archive3/powers.htm
>>
>>Mike-KK4MS
>>a_borg at yahoo.com
>>
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