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:
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{}-->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 RadabaughAmplex22690 Pemberville RdLuckey, OH 43447419-261-5996
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 PMTo:
[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 PMTo: [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.
