480 PS dead again

Wizards,

I have been gone from my plant for a while and upon returning I have two, 480vac-24vdc power supplies on my desk with DEAD written on the box.

Upon investigation, it turns out that one of the two power supplies in this machine have died.
When the PS dies, they notices that fuse leg 1 is also blown but the other two are just fine.
They replace all 3 fuses and the PS, everything works out great for an undetermined amount of time.

We are not in production on a daily basis atm and most of the time the machine just sits idle. When we do run the machine, everything works out just fine, we just randomly find a dead power supply in it in the morning when we show up.

A line conditioner was asked about, but I am reluctant to add more things to this machine without having a better idea as to what the root cause is.

I would add a line filter immediately. If the power supply output were overloaded or shorted to ground then it would shut down to protect itself, and normal use of the DC supplied would never trip an incoming fuse.
Dirty power from a nearby machine can do very strange and wondrous things in control panels. I even had a laptop report a bad battery & refuse to charge, then my UIC wouldn't work - reported as a bad USB device by windows. Took them back to the office & the battery was good again & the UIC worked. Went back to the machine without plugging in the AC cord & it worked, plugged it into the programmer outlet and the battery & UIC both suddenly died - plus they reported PLC problems a lot on that line. A line conditioner on the PLC power transformer solved all 3 problems.

Beg, borrow, but not steal , a 3 phase voltage recorder, I recon you will be surprised by what happens over night.

So you have 2 dead power supplies and both had the fuse on leg one blown? Were they both in the machine at the same time, or one was replaced, then the second also failed the same way?

I'd also recommend a line conditioner. Just so you know the power coming in is clean. I install them on every panel that has a 480 connection in the panel.

Engineerj22,

The power supplies were replacements as they failed, we are only dropping one at a time.
I will also look into a 3 phase voltage recorder to see what I can see.
I think we are going to move forward with a line conditioner, as it seems you all recommend it.

Thank you,

Gad.