Power factor of zero... fun. I am still pissed off at a teaching assistant that marked an exam answer as wrong (only one wrong on that exam).
The question: What is Power Factor. My answer: The cosine of the phase angle. I was right then, I am still right. 30+ years has not changed anything. From: Mark Radabaugh Sent: Sunday, January 08, 2017 1:22 PM To: af@afmug.com Subject: Re: [AFMUG] OT in search of 400/230 VAC I was amused at the fellow students who could tell you anything theoretical about inductors and capacitors would be the same kids in power lab who would do something stupid like pull a banana plug jumper off of a running DC motor and shit themselves when the arc burned the end of the plug off. The school had a pair of 10Hp (maybe bigger) motor generator sets along with all the controls to allow you to synchronize and parallel the gensets. So for a class we are doing exactly that. Get done and the professor wants us to decouple them. “Just turn that knob there so that the power factor is back to 0 first”. Student looks at the professor weird and the professor says it again so he starts cranking the power factor toward 0. Then it got real noisy with some interesting oscillation noises - thought both gensets were coming off the stands. “Wait, Wait - I meant 1, not 0”. Memorable if nothing else... Mark On Jan 8, 2017, at 12:52 AM, Chuck McCown <ch...@wbmfg.com> wrote: I had drafting and a class called “geometric dimensioning and tolerancing”. I wish I could remember all those symbols because I still run into them on mechanical drawings all the time. AutoCAD just been invented when I was in school and we used it only for PCB layouts. I made salt water rheostats all the time as a kid. Another class shorted a generator. It tore itself off its mount and launched across the room. From: Ken Hohhof Sent: Saturday, January 07, 2017 7:40 PM To: af@afmug.com Subject: Re: [AFMUG] OT in search of 400/230 VAC 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:af-boun...@afmug.com] On Behalf Of Mark Radabaugh Sent: Saturday, January 7, 2017 8:18 PM To: af@afmug.com 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 On Jan 7, 2017, at 8:58 PM, Chuck McCown <ch...@wbmfg.com> 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: af@afmug.com 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: af@afmug.com 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.
