For my schools BSEE everyone had to take power and the lab. Most hated it, I actually liked it. The 'lab final' the professor made us take wasn't his best idea. Lab was in the basement and I'm taking the second session. Elevator doors open to the basement and the smell of burnt electrical gear is strong. Professor walks out with a armload of of test equipment headed for the repair shop shaking his head and mumbling 'not a good idea, bad idea'
Mark Radabaugh Amplex 22690 Pemberville Rd Luckey, OH 43447 419-261-5996 > On Jan 7, 2017, at 8:58 PM, Chuck McCown <[email protected]> wrote: > > In college the only guys that got the 3 phase classes were in the power > engineering track. I don’t recall a single lecture or homework assignment > about it. > > From: Chuck McCown > Sent: Saturday, January 07, 2017 6:49 PM > To: [email protected] > Subject: Re: [AFMUG] OT in search of 400/230 VAC > > Had to learn me some 3 phase stuff... if going from delta to Y there is > indeed a square root of three applied to the turns ratio. > So if I take a hacksaw to the primary and convert it to a Y, then the > original turns ratio should reappear. Should.... > > From: Chuck McCown > Sent: Saturday, January 07, 2017 6:05 PM > To: [email protected] > Subject: [AFMUG] OT in search of 400/230 VAC > > 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.
