seeing your three phase overheads reminded me of a visit to a farm many years ago where an ancient old boy in plus fours showed us a problem with his 3 phase mill mixer unit, when it failed to start, and growled, we immediately sussed it was off a phase, but the old boy said "nay lad, thats summat else" grabbed a long peice of wood, wandered outside and began to poke at the line taps on the overheads! when the guy I was with shouted at him to stop, he said "Why its areet as long as't woods dry, otherwise appen thoo'l get a tickle off'n it!" Needless to say we fixed the problem (star delta coil failed on an old Memota side handle starter) and also refitted all the line taps so he didnt get fried!
Phil