Don't know about this in the "real world" but I remember reading that there needs to be a transformer to adjust the supply voltage before entering the converter, to ensure the correct three-phase voltage (208?)...
is the 167V at the breaker? Have you tested if the three-phase is balancing properly?
If the supply voltage drops at the breaker, I would guess first that the problem is with the supply, and that the extra load is bringing the problem to the surface. It's probably either the PoCos problem, or you have a bad connection on your side.
Try tightening all lugs on your mains coming into the panel, and everywhere else that you can get to. Make sure all the busses are in good condition and that your breakers are seated properly and the contacts are all in good condition.
If that does nothing, call in your PoCo to check their connections at the x-fer and behind the meter (if you can't get behind the meter yourself because they have it locked out). ALWAYS BE THERE WHEN THEY COME OUT so you can show them the problem UNDER LOAD, or they will not see the problem at all.
I see this problem a lot pretty often,and it's usually a loose connection or a bad main feeder.
IT IS ON THE RAILROAD .. WE ARE GOING TO BRING IN GENERATOR IF WE CAN'T FIND A PROBLEM. I AM JUST WONDERING IF I HAD A BAD STARTER WOULD THIS CAUSE THIS.. I AM NOT ELECTRICIAN BUT HAVE GENERAL KNOWLEDGE. WHAT ABOUT THE PHASE CONVERTER ITSELF ? THANKS FOR YOU HELP