Running 3 phase 780s on single phase power

[Rich Alderson]

> From: Guy Sotomayor
> Sent: Tuesday, January 20, 2009 1:06 PM

> On Jan 20, 2009, at 12:35 PM, Rich Alderson wrote:

>> The KL-10, like other DEC gear, uses 3-phase input power as the
>> simplest way to get lots of amps into the system:  60A @ 208 3-phase.
>> All of this feeds into a single gigantic boat-anchor grade
>> transformer which forms the basis of a linear power supply.  2/3 of
>> that power goes back out as simple heat.

> Umm.  No.  That transformer is a ferro-resonant transformer.  It
> *needs* 3-phase to work!  It supplies the basic 12v DC that are then
> used to by the linear regulators.  It's those that burn the power as
> heat.  Replacing the linear regulators with switchers will reduce the
> consumed power by a lot.

And that's why I let the EEs deal with designing alternative power
systems.  I knew that there was a linear component to the entire system
that wasted a lot of power, but thought that that started at the
transformer.  I'm a software/sysadmin with an occasional need to pick up
a soldering iron--which I usually hand to one of the others.

Thanks for straightening me out, Guy!


Rich Alderson
Server Engineer, PDPplanet Project
Vulcan, Inc.
505 5th Avenue S, Suite 900
Seattle, WA 98104

mailto:RichA at vulcan.com
(206) 342-2239
(206) 465-2916 cell