3-Phase Explained ( Commerical Electrical )

[Bob Badger]

http://terraserver.microsoft.com/add...er%2c+PA+17517

It happens Terraserver has a photo taken during constrution, you can see the ell shape of the main building.

[Paul W. Abernathy]

Please do so.....

On the data center....Can you possibly imagine the harmonics that could take place with all the computer systems being plugged in. I hope the neutral was atleast double sized on that one feeding the data center...thehehehe

I tell you.....we have come a long way in knowing the effects of harmonics in the way of heat over the past 10 years...only seems to really present a problem on unbalanced Wye systems...but I have heard some peers say Delta are prone to it as well...but since in deltas the neutral cancels out to balance itself not nearly the issue which is why I think in the NEC all the references to harmonics point to WYE systems only.

I can only imagine the time you spend balancing that out if you had to do the panel schedule on that. I did one nearly that size some 15 years ago and the electrical engineer made ME size out the transformer, panel schedule and balancing when normally it is done on the plans by the engineer...talk about sweating bullets ( i was only 21 years old heading up that job )

[Paul W. Abernathy]

COOL bob....but you have NOW damaged me.....I can't stop playing with the Taraserver thingie....I have now looked at all my old girlfriends homes so see if I happen to be in the picture..the moment their father threw me out of the house...

[Bob Badger]

90% of the buildings we build will have 480Y/277 services with the neutral conductor size matching the other conductors.

We will bring 480 delta right to the computer rooms to feed a "K" rated transformer. Once we leave a 480 delta 208Y/120 transformer we will often be running double neutrals for the harmonic issues.

Often the specs will require separate neutral for each branch circuit or if we can run multiwire branch circuits the neutral will be one size larger than the other conductors.

The panels that feed the non-linear loads will be ordered with 200% neutral so a 225 amp panel ends up with a 450 amps neutral bar fed with double neutral conductors.

[Bob Badger]

Yes Terraserver is a big distraction.

I can find my own house, most photos are from about 1995

[Paul W. Abernathy]

lol...I know..in fact when I looked up MY house it was not even their...I built my house in 2001 and the image to the area where my house it was a big field..lol.....ahhh it bought me back to the first day i walked the field and said..this is where my house will be......lol

Ahhh...yes.....thank goodness for the NEW transformers that reside in K factors..lol....build to handle the oncoming harmonics factors...you see...they are learning more and more about them every day.

You guys are GOOD......you have sized it to meet any possible need...man I need you down here so I can build my commerical side of the business bigger...lol....good people are hard to find.

[Bob Badger]

The power a modern office / research building uses is staggering.

We did a building for a pharmaceutical company the service was 13.8 KV and would often draw 150 amps.

Thats about 3500 KW or in house service terms (240 volt single phase) about 14,000 amps!

[Bob Badger]

Originally Posted by pabernathy

You guys are GOOD......you have sized it to meet any possible need...man I need you down here so I can build my commerical side of the business bigger...lol....good people are hard to find.

Well thanks we do have some great guys but we also work on well engineerd projects.

Have to give the engineers their due.

But we can 'wing' it, the plans I was handed for the 3000 amp serice change with the large transfomer where a simple one line riser diagram quickly drawn by the project manger on one 8.5 x 11 sheet of paper. I had to figure the pipe, wire and layout.

[Paul W. Abernathy]

Thats the part of the business end up doing and takes much of my time. Many of the commerical jobs do not want to pay the engineers to do the electrical calculations for these type of things anymore...figure they can cut that cost out and except the electrical contractor to do it...

Happening more and more...and in commercial jobs these days I get tired of playing electrician and electrical engineer as well.....I like commercial plans that are already layed out and the electrician just follows the plan...sad to say getting less and less of those detailed plans..."SIGH"..the good news is I am doing less and less commercial jobs...YAAHHHOOO

[Greg Fretwell]

For some reason Naples Fla has a lot of red leg delta. It will throw you if it is the first time you see it. We were having a lot of problems with some equiplment there until I figured out it was wired 208 wye.

[Paul W. Abernathy]

Greg,

Yeah...no doubt...

Back years ago they would put the high leg on the C connection and over years moved it to the B connection.....and as the time went on the new panels are added and it still has a old system at the transformer under control of PACO....then the electrician ( new one ) replaced the panel schedule and then follows todays requirements for placement and marking and well....next thing you know...everything that is on the center line is BLOWN.....all because of a change from the high leg position in the years before they started standardizing it.....see that alot in older 3 phase construction that is being updated to newer.

Yah....I always tell the young electricians to always test line to line in a secondary panel....line to ground should read 120V but line to line should read 208V in a normal WYE setup.

Same as in a delta....test from the B line to the C line which is normally the 120V phase line.....it should give you 208V which means it is a Delta with a high leg....but any line to line will be 240V.

Anyway......as I am sure you do as well....we see it all the time and if you have no basics in 3-phase it can get confusing for someone new in the industry.

[Greg Fretwell]

We got in trouble because nobody at IBM had ever seen delta. The plugs were the same and everything powered up normally. A lot of the stuff really didn't care. We did have tape drive controllers with ferro supplies and they were burning up. I got involved on #2 or #3.
The funny thing was some of the equipment was plugged for 240 so somebody must have noticed. It just wasn't everyone who worked there. This was a customer who bought used equipment so it could have come in plugged that way.