I had a good Google of this but I think I need help from the experts to fully understand what's going on here:
So yesterday one of my colleagues was doing a show in a large old warehouse space. He plugged in the distro to the 32a 3 phase socket provided (we are in Australia, so 240v). The metres on the distro read 240-250v phase to neutral which is normal. I think they then plugged in some equipment which didn't power up, so he goes to the distro to investigate.
He found that with everything unplugged from the distro (ie no load) and the main 3 phase breaker on it still reads 240v, but each time he turns on a breaker for an individual circuit that phase drops to 50-75v and the other 2 phases go up to 300v or more.
Is this because there is no neutral (wye 3 phase with no neutral for motors/welding) or is this what happens when you plug a wye config distro into delta 3 phase?
It matches a description of a floating neutral, but I can't think why it would happen with no load?
They obviously should have metered the mains first, but in this case would that pick up the problem, given that the distro didn't initially show any strange readings on its meters?
Also there seems to have been some damage to the distro, the breakers now trip immediately. What would have caused this?
Any help would be greatly appreciated so I can understand how to spot something like this when checking mains. Thanks!