"T" wrote in message
...
Good info, (you must be in europe, 220v!) I will test the UPS circuitry. I
think I need to find a 'sensor' to detect the charge build up on the
boards. Somehow if the supply voltage is not the nominal 120vac and is
instead 180vac or so, somehow the regulators are developing tremendous
voltages on the circuit board to jump those gaps.

"Eric H" wrote in message
...

"T" wrote in message
...
A raised floor server room with 6 servers, fiber optic patch panels,
large control system cabinets and large UPS system, has been recently
been plagued by computer power supply failures. The supplies fail when
apparently many tens of thousands of volts jump from inside the PS around
the switching regulators to the chassis of the supply taking out all the
components. This has happened to 8 supplies so far. A visible blue flash
has been witnessed several times by pewrsons in the room.

The servers so far affected are all sitting on the raised computer
center floor. What ususally happens seems to be when a person enters the
12x20ft room or gets near a server a large snap is heard and the server
is on the backup redundant PS, if it has not already failed.

We have been adding grounding bonding from all computer case to the bldg
steel, raised floor structure, etc to try to stop this. Its still
happening. The computers are various brands and varoious ages, from 1
week old to 5 years old. The probelm began occuring 2 months ago. The
data center was built 12 years ago.

We are at a loss to figure out how the charge is building up on the
inside of the power supplies. I am thinking about the common power
source, via the power cords Hot, Neutral and Ground conductor.

The green wire should be bonded to the PC case. Apparently the PS
regulator board floats above chassis potential. Apparently a large
potential differnce is building. It jumps a 1 inch gap to the chassis.
Burn marks from repeated arc overs are evindent (the arc that makes it
fail is not the 1st time it occurs!)

The Hot and Nuetral..how could a charge be coming in on these conductors
and getting past the MOVs to build a potential on the boards.


Any ideas would be appreciated.
TJS





I have had this problem before. The servers on site were blowing power
supplies intermittently and corrupting the data on the HDD. After lots of
parts swaps, softeware rebuilds etc the situation was getting extremely
serious. I was called in to investigate.
The site had a large UPS installed. Measuring the voltage with my
digital meter I found the supply varying from approx 198v to 224v over a
period of 1 hour. The UPS was isolated but the readings were very
similar.
I temporarily installed a mains analyser and when I returned a few days
later, after looking at the printout was amazed to find that the power
was fluctuating between 210v ~ 380v. It should be 220v.

I had a qualified electrician check out the site but he could find no
fault. I then called out the electricity board who discovered an
intermittent open circuit earth in the buildings 3 phase 415v power
supply.

This was traced to a connection outside the building underground. After
repair we had no more problems.


Measure the mains input with a Digital meter to check if it is within
specification for your country.
Then hire a mains analyser for a few days to monitor the supply. I presume
you have 3 phase supplies going into the building as we do in the UK. your
problem appears to be a mains supply problem.