Sounds like PM is single phasing
I know you said you checked it though

Building taking a power hit??
Emergency generator???

Bad BD relay?

I have tons of problems with PM contactors on mce cars especially with the aux contacts on them. I believe theres is an input to the drive based on those aux contacts on the PM contactor. Try to duplicate the fault by pulling one of those input wires off of the aux contacts and see what fault pops up when the PM contactor engages. This problem sounds familiar. I'm sure your brake pick and hold is good. The single phasing is possible but I doubt You would here our favorite humming sound. Also dont trust your meter on ohms w/o power on reading those aux contacts its all about the load those contacts can handle when engaged. Good luck.

Just a suggestion, try loosening and re - tightening all the drive connections. Had a mce with a hpv 900 drive do similar things. One of the phase wire lugs seemed tight enough, but the wire welded itself to the loose lug.

Thank you for your suggestions gents.

I'm babysitting the unit for the second day. Wahoo!

Postal, I was able to see all 3 phases before trying to check the brake. That was my initial thought as well. Great minds think alike. 🙂

Sccjr, I lifted B1 and boy does it seen familiar... I'm replacing all of the aux contacts tomorrow after I pick them up. They are showing signs of wear.
Always great advise not to trust the ohm (continuity) readings of a meter. I prefer reading voltage myself. Checking the voltage drop has served me well.

Galaxy, I'll check it out thanks...

Thanks again,

Turned out to be the BR relay. #3 BR contact in the brake coil circuit would fail with no pattern or rhythm. Some times it would be weeks before it would fail. Finally I pulled the relay off the controller and opened the coil & armature up. When I did some debris fell and hit my foot. Looking at the contacts there is some burn. But there is a needle like tip formed on the contact. As if the contact metal heated up and was drawn the follow the arch across the contacts. I'll post a picture if I can figure out how.

Thanks again Brett for you suggestions. Your a good Mate...

No probs JKH. Glad to help in any way. When a main switch trips its nearly always a brake issue and a inrush overload on a vf drive is probably similar thing and good to remember.