This was not one of my units, but I saw the aftermath.
Here is the short list.
248V between the metal wall and ground. Which was first noticed by the guy leaning against the wall. Then he touched it again "just to be sure it was live."
This also destroyed the PLC, the VFD, exothermically welded the power block to all of the wires connected to it, and welded the portable heater to the deck.
The fan runs CW through remaining VFD and CCW in bypass?
Tops of main fuses melted, but fuses did not blow? Maybe the arc flash from adjacent power block melted them?
Odd thing was that when they tested the questionable leads to ground there was no continuity. This was before it blew.
Maybe a split in the insulation waiting for enough potential to jump to the conduit? Maybe said insulation was stretched thin, then melted through when energized.
Lab guy was almost in tears. I told him he should take the burned out parts to his boss then ask for a couple of days off.
This was a huge unit and will probably take a week to comb through for any more problems and fix the current problems.
As a side note on my unit the guy doing the cannon plug managed to get almost every pin in the wrong spot. I repaired it myself and told him to ohm out every wire on the entire unit before he proceeds. Then I would do it again myself when he was done, before testing. I guess he didn't understand when I told him one wrong pin could blow up around ten thousand dollars worth of the governments equipment. I hate hawkeyeing people but this stuff has to be perfect the first time around.
So, how was your day?
