Defective run? Or counterfeit GE 277 volt breaker?

[hillbilly1]

One of my guys from a previous employer called me today saying he was having issues with a single phase step down transformer. He said the primary voltage goes to zero when the transformer is connected (1kva). The transformer is mounted to the side of the panel, and has another just like it mounted on the other side of the panel. Both are doing exactly the same thing, and are on separate circuits. Breaker is not tripping. I had him move it the other phases, same thing. Voltage from the panel busses good phase to phase, phase to neutral, phase to ground, with no voltage neutral to ground. He has no other spares to try. It would be really odd that he has two bad breakers, everything is new including the panel. Only two other loads in the panel, two 90 amp three poles for two three phase EV truck chargers, and he says those are working. Forgot to have him do a fop test on the breaker, but he said the buss voltage remained good with that transformer connected, just the breaker output went to zero.
The customer supplied the equipment, and is a well known importer of Chinese goods. I’m wondering it they may be counterfeit breakers?

 

[augie47]

Single pole breaker ??
If so and he's measuring to ground... possibly an ungrounded system and once a load is applied the ghost voltage drops to zero... ???? obviously a shot in the dark

 

[hillbilly1]

New info, found out it’s feed from a delta wye isolation transformer, and now they are telling me the chargers are bringing all three phase down to zero. They are getting 277 to ground from each phase, 277 to neutral from each phase and 480 phase to phase. Something is up with that isolation transformer. They are supposed to send me pictures. Service voltage is 480 wye, apparently the engineer wanted an isolation transformer in the mix, maybe to reduce surges from the poco? Southern Florida, so that may be it. I’m betting maybe the isolation transformer is mislabeled, and is reverse fed, and since the secondary is bonded, that may be why they are getting 277, it would be from the poco service. Supposed to send me pictures in the morning.

 

[hillbilly1]

Manufacture said the new isolation transformer was bad, and was sending another one. Apparently they have had this problem before.