[c-nsp] 7609 6000W-DC PWR supply cabling Question

[Justin Shore]

Justin M. Streiner wrote:
> On Mon, 31 Mar 2008, William Jackson wrote:
> 
>> The 6000W-DC power supply takes four pairs of 4AWG PWR cables, my
>> question is the following.
> 
>> Which way is this setup cabled?
> 
> I would think in a DC environment you'd want all of the circuits for one 
> power supply to come from one breaker panel, but separate breakers, then 
> feed the second supply from another breaker panel.  The reason for this 
> is that if you feed one supply from more than one breaker panel, the power
> supply might be taken out of service if it's only partially energized. 
> I'd think you would want the feed from the rest of your DC distro plant to 
> the breaker panel to be sized and fused high enough to handle the 
> combined draw of all of your output circuits, or whatever margins are 
> dictated by your local building/electrical codes.

That's prettty much it.

The DC PSUs will continue to operate without all line-in feeds being 
hot, assuming that their combined sum is great enough to handle the 
load.  Our 4000w DC PSUs require 3x 40a -48v circuits per PSU.  IIRC the 
4000w PSUs will operate with only 2 of the 3 feeds hot.  We fused each 
line-in separately on 40a breakers.  The chassis received feeds from A & 
B sources separated by PSU.  Grounds were common.

4awg is much easier to work with than 00awg.  It's also generally 
cheaper per foot to do 3x or 4x 4awg than 1x 00awg.  The cost for a pair 
of 125a or 150a 00awg breakers cost far more than that of 6x or even 8x 
4awg 40a breakers.  Most people don't have the resources to crimp 00awg 
lugs either and have to call in electricians.  We're a DC shop and IIRC 
even we call in someone with a hydraulic crimper to do those.

Justin