Meant to say I wouldn't have a chance to figure it out WITHOUT a diagram...
On Sat, Jan 7, 2017 at 7:16 PM, Bill Prince <[email protected]> wrote: > Deltas, Whys, those were all Greek to me. I wouldn't have a chance of > figuring it out a diagram. The phase shift is the hardest part. > > > On Saturday, January 7, 2017 6:40 PM, Ken Hohhof <[email protected]> wrote: > > > Closest I had was “Electromechanical Devices” but nicknamed “Motors”. The > professor with the least seniority got stuck with teaching “Motors Lab”. > After the year I took it, they eliminated it as a required course, along > with Drafting. (No, not AutoCAD, the pencil and paper version.) They had > eliminated Surveying as a required course the year before me. > > The guy I had for Motors Lab really, really didn’t want to be there. His > answer to any question was “Let’s find out.” Student asks, what happens if > you open the field coil on a motor? Let’s find out! Student asks what > happens if you throw a dead short across the output of the generator in a > motor-generator pair? Let’s find out! That’s also where I was introduced > to the water rheostat as a dummy load. > > I suspect Chuck would have volunteered to teach Motors Lab. But still > “Let’s find out!” And wearing a lab coat. And safety goggles. > > *From:* Af [mailto:[email protected]] *On Behalf Of *Mark Radabaugh > *Sent:* Saturday, January 7, 2017 8:18 PM > *To:* [email protected] > *Subject:* Re: [AFMUG] OT in search of 400/230 VAC > > 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 <(419)%20261-5996> > > 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. > > > > -- -- bp part15sbs{at}gmail{dot}com
