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William K.
User Rank
Platinum
The "Y -Delta" goof
William K.   8/17/2013 7:47:52 PM
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Getting the connections wrong, Y instead of delta is one of those things that I have learned to always add specific instructions to the drawing about, just because it is not always clear which should be done. It also makes a big difference on motors and heating elements, and that can lead to unanticipated problems that are not so very simple to solve.

AnandY
User Rank
Gold
Re-PYTHAGORAS
AnandY   8/11/2013 4:17:56 AM
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A very interesting post. It is a concept that many have probably forgotten about but it really applies in the real world, most of the concepts that we learn in the education ladder are very relevant in the normal roll of life. They maybe disputed to have no relevance but they eventually get you off guard and help you in a big way.

AmirZohar
User Rank
Iron
Re: PYTHAGORAS
AmirZohar   8/5/2013 12:23:09 AM
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Thank, Tom-R for the good example. Electric motors and generators are in deed fascinating machines in so many ways. Even though the basics are always the same, and it's all based on the simple IxR=V, there is so much mathematical and practical depth and beauty to it. 

oldtimer8080
User Rank
Gold
Good old mathematical to electronic relationship: using the right tools
oldtimer8080   8/3/2013 4:34:17 PM
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This incdent broght meback to my youth and the first Dranetz datalogger.

For a time, I lived on a dairy farm located on the end of a stub line for a local electric co-op. The power was always marginal and adding or reducing motor loads would cause all of the lights to flash and then dim while the multiple horsepower electric motors were switched on and the same flicker would happen when they would be switched off.

We finally had a Dranetz Chart Recorder put on our stub end and left on it for a week. I was fascinated by that chart recorder even then and watched and heard the little " click " as a data point was added to the tape....

I now know what an LCR nightmare it was for the engineers to resolve most, but not all of the farm's problems. And people did not know about stray voltage ( actually current flow causes the problems )  then!

 

wbswenberg
User Rank
Gold
Reactive Power
wbswenberg   8/2/2013 5:45:33 PM
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I was involved with some of the power systems on the 777.  In regards to the power lab it was desided that we needed a data aquisition system rather that discrete insturments.  I checked some's other work besides doing my own.  I recived some very odd voltage and current measurment that were being used to determine power and power factor.  it was just not working out.  So I asked about how they collected the data.  As soon as someone said data system I know what was worng.  Its a time sampled measurement and unless it is measured directly it can not be calculated as it is not the same instance.  We put a Dranetz power analyzer on the system and got the information we needed.  

notarboca
User Rank
Gold
Re: PYTHAGORAS
notarboca   7/28/2013 9:31:13 PM
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I'm with you, bobjengr.  This is such a good example of analytically troubleshooting.  So glad I held on to all my mathematics books from high school/college--they come in handy!

Tom-R
User Rank
Gold
Re: PYTHAGORAS
Tom-R   7/25/2013 11:01:24 AM
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Great example of problem solving that could be used in an electrical or math class to demonstrate something real in the numbers. I'm a mechanical engineer so I had basic electrical courses, but I'll admit 3 phase power with delta or Y connections is best left to an electrical engineer instead of me. You're story reminded me of one of my projects though. I was managing the installation of a packaging line and the electrical engineer came into the site office. He was moaning that we had to rewire most of the motors to switch the phases. Of the 30 motors 22 were running backward. So to lighten the mood I jokingly said he should ask the utility to switch the power they were sending us. Apparently I was a genius; or at least I was told I was. The electricians switched two of the phases supplying the motor control panel and we now only had 8 motors to rewire. Delta or Y doesn't matter to me, I still find 3 phase power amazing.

AmirZohar
User Rank
Iron
Re: PYTHAGORAS
AmirZohar   7/25/2013 1:22:14 AM
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From all the good things we learn in the graduate studies, it's surprising how few we end up using in the engineering world. Don't you think? We were looking at this problem with a large group of experienced field and systems engineers. Yet it's so hard to think about anything beyond simple linear relationships. Even after I decided to check the Apparent Power values, I had now idea what will come out... I plugged in the numbers, et voila! I enjoyed almost all the things I learned in my advanced studies. but rarely do I come across opportunities to apply them as an engineer. Thankfully, this case worked out pretty nicely. :-)

bobjengr
User Rank
Platinum
PYTHAGORAS
bobjengr   7/24/2013 5:25:22 PM
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Excellent post Amir.  I had a mechanics professor who told us "if you guys would stay long enough you could learn enough to get you through to the end of your working life".  You would not need an MS or even a doctorate.  He just could be correct.  One of the very books in my library is my high school trig book.  I seem to go back and back and back when I need that type of information.

Ann R. Thryft
User Rank
Blogger
Re: It's all numbers
Ann R. Thryft   7/23/2013 5:42:58 PM
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Amir, I think it was a perfect teaser. In fact, Pythagoras is best known among moderns for the hypotenuse theorem. I like your description about staring at all the numbers until this deceptively simple ancient equation clarified things. I think he would smile not just because his theorem helped you out in the pure math sense, but also because he thought that the power of numbers and their relationships underlay the structure of the universe.

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