Stubborn dude... Wear the proper protection and don't work alone. No seas terqo
On Jan 7, 2017 6:06 PM, "Chuck McCown" <[email protected]> wrote: > OK, last month I tried to use a 240-208 transformer to convert 480 to > 400. Transformer complained and that poor old 480 circuit breaker just > would not cooperate. > > So, today I have a 240 to 480 delta to delta. I rewired the 480 side to Y > by joining all the taps. > Feeding 208 in the 240 side should have given me 416 volts... one would > think. > > First try, the transformer made lots of noise the the wires were dancing > in the conduit. Probably means something is wrong. So I disconnected the > Y connection and just had three windings on the HV secondary. But I was > getting 720 volts instead of 400. Hmmm.. > > OK, not understanding something here, but it is off by a factor of the > square root of 3 so it is a three phase problem and I would have to break > out a book about phasor diagrams to understand it. I did discover that if > I connected all the outputs and left the taps floating it remained silent. > If I connected the taps and left the outputs floating it grunted loudly. > Don’t understand that either but I am sure it has something to so with > phase relations. > > So, thinking that the transformation ratio changes by the square root of 3 > when you go from delta to Y, tomorrow I am thinking of converting the > primary to Y so we are Y-Y and hopefully the original ratio will > re-appear. > > I will be feeding it from a 208 delta circuit. > > This will involving taking a small hack saw to those huge square copper > windings on the primary side to disconnect them from each other and tie > three ends together. So kinda kills the resale value of the transformer if > it does not work. > > So far, no smoke, fire, arc flash or electrocution. I was using a fluke > voltmeter on 720 volts and bare hands though..... > If I make my wife a widow, please nominate me for a Darwin. >
