PDA

View Full Version : 3 phase banks



Maineiac
06-14-2008, 02:23 PM
I was wondering what the procedure was in hooking up a 3 phase bank. How do you connect the transformers together, i know there is different voltages you can get but what is the most common ones. Also what is the process of testing the rotation consist of ?

Special ED
06-14-2008, 07:39 PM
Boy did you just open a can of worms! lol Theres so many ways to make connections. Depends on the primary system and what kinda secondary volatages you need. If your a green horn ape don't worry about this stuff just yet. You have so much to learn before you get into banks and connections and trying to learn this stuff too soon just leaves alot of apes confused or in the dark completely.

swetngblts
06-14-2008, 08:03 PM
I was wondering what the procedure was in hooking up a 3 phase bank. How do you connect the transformers together, i know there is different voltages you can get but what is the most common ones. Also what is the process of testing the rotation consist of ?

We're going through transformers at NLC right now so let me take a stab at this.

Open or closed bank?

What are the transformers asking for?

What does the customer need?

MEGA81
06-14-2008, 09:58 PM
120/240, open delta. H1 of trans#1 to a phase, H2 of trans #1 to b phase, H1 of trans #2 to b phase, H2 of trans #2 to c phase.

120/240, delta, H1 of trans #1 to a phase, H2 of trans #1 to b phase, H1 of trans #2 to b phase, H2 of trans #2 to c phase, H1 of trans #3 to c phase, H2 of trans #3 to a phase.

120/208-277/480 wye, H1 of trans #1 to a phase, H2 of trans #1 to neutral, H1 of trans #2 to b phase, H2 of trans #2 to neutral, H1 of trans #3 to c phase, H2 of trans #3 to neutral.

If the pots are hooked up three phase wye on the primary side, and the secondary sides are delta, the H2's are floated. Alright lineman, how did this apprentice do?

Maineiac
06-15-2008, 07:52 PM
On a closed Wye-Delta 240v straight power bank wouldnt you tie the h2's together with the system neutral instead of floating them? I know a Wye-Delta 120/240 bank is the hooked up the same as a straight power bank but it has a ground on transformer 1 at the x2 bushing. Im just looking through some of my bookwork on transformer connections and i dont understand why its Delta on the secondary side if you connect a neutral. I thought delta didnt use a neutral? And if your using a floating wye-tie and its not connected to the system neutral how is this realy a wye connection? I guess i dont understand Wye-Delta that well if anyone has any advise that be great. Also ive noticed that all the secondaries are color coded with marking tape, i know this has to do with the rotation but how do you do it? Im a 5th step apprentice and all ive hung so far is single phase transformers.

PA BEN
06-15-2008, 08:25 PM
Always float the High side H2's. If you loose a transformer it well single phase and you well know you have a problem, if you tie it down you well have a open delta that is 57.7% of the bank.:rolleyes:

swetngblts
06-16-2008, 12:01 AM
Correct me if i'm wrong here.

In the Transformer Lab we mark the secondary side with red, white, and blue tape. Red and white being the 2 hot legs and the blue being the Power leg. If the rotation needs to be changed it's done on the red and white hot legs. Don't confuse the power leg (blue tape) with a hot leg.

RadonHuffer
06-16-2008, 03:40 AM
http://albert-cordova.com/Y.jpg

http://albert-cordova.com/delta.jpg

I scanned them in at different times from an old book called The linemans and wiremans handbook.

I have seen some stuff grounded on subs that I did not understand? The Engineer signs off on that part.

MEGA81
06-16-2008, 04:49 AM
Dont forget to alley cat bad dog the winding leads. A and C on x2, B and D on x1( or x3 if its subtractive). Should have put that in the original post.

lewy
06-16-2008, 05:49 PM
Correct me if i'm wrong here.

In the Transformer Lab we mark the secondary side with red, white, and blue tape. Red and white being the 2 hot legs and the blue being the Power leg. If the rotation needs to be changed it's done on the red and white hot legs. Don't confuse the power leg (blue tape) with a hot leg.

On a 3 phase hookup your rotation can only go clockwise or counter clockwise .
If you want to change the direction you can change any 2.
As far as markings go we use red white & blue but it could be anything some people use A B C .
You want to be careful with colours because where I come from electricians use white as there neutral.
This one is for Maineiac you can have 1 neutral only on your delta secondary(for lighting 120 V) as there is no reference to ground, hookup the second neutral & you would have a short.

Pootnaigle
06-16-2008, 07:49 PM
120/240, open delta. H1 of trans#1 to a phase, H2 of trans #1 to b phase, H1 of trans #2 to b phase, H2 of trans #2 to c phase.

120/240, delta, H1 of trans #1 to a phase, H2 of trans #1 to b phase, H1 of trans #2 to b phase, H2 of trans #2 to c phase, H1 of trans #3 to c phase, H2 of trans #3 to a phase.

120/208-277/480 wye, H1 of trans #1 to a phase, H2 of trans #1 to neutral, H1 of trans #2 to b phase, H2 of trans #2 to neutral, H1 of trans #3 to c phase, H2 of trans #3 to neutral.

If the pots are hooked up three phase wye on the primary side, and the secondary sides are delta, the H2's are floated. Alright lineman, how did this apprentice do?
I'd say youre bout 50 %......... Most of the transformers I have dealt with also have some X bushings and I dont bleve you adressed them at all. So you got the hi sides all hooked up.......... opps low side needs a lil work

Trbl639
06-17-2008, 05:09 PM
Correct me if i'm wrong here.

In the Transformer Lab we mark the secondary side with red, white, and blue tape. Red and white being the 2 hot legs and the blue being the Power leg. If the rotation needs to be changed it's done on the red and white hot legs. Don't confuse the power leg (blue tape) with a hot leg.

Forget the red/white/blue tape..it can get ya in trouble.............as someone said, most electricians use white to designate the neutral.................also, a lot of electricians use either red or orange to designate the wild or high leg............as the NEC states, red or orange for the wild leg..............the best way to marks secondary is...........

Neutral, if it is not bare conductor, WHITE.........
A phase.........1 wrap of any color tape......other than white
B phase..........2 wraps od any color tape...even the same color as A phase
C phase..........3 wraps of tape.......also the best way to designate the wild leg

example..
neutral........ white
A phase.........1 red
B phase..........2 red
C phase..........3 red


It's awful hard to go wrong with 1-2-3!!!!!!!!!!!!

MEGA81
06-17-2008, 07:05 PM
120/240, open delta. H1 of trans#1 to a phase, H2 of trans #1 to b phase, H1 of trans #2 to b phase, H2 of trans #2 to c phase.

120/240, delta, H1 of trans #1 to a phase, H2 of trans #1 to b phase, H1 of trans #2 to b phase, H2 of trans #2 to c phase, H1 of trans #3 to c phase, H2 of trans #3 to a phase.

120/208-277/480 wye, H1 of trans #1 to a phase, H2 of trans #1 to neutral, H1 of trans #2 to b phase, H2 of trans #2 to neutral, H1 of trans #3 to c phase, H2 of trans #3 to neutral.

If the pots are hooked up three phase wye on the primary side, and the secondary sides are delta, the H2's are floated. Alright lineman, how did this apprentice do?
I'd say youre bout 50 %......... Most of the transformers I have dealt with also have some X bushings and I dont bleve you adressed them at all. So you got the hi sides all hooked up.......... opps low side needs a lil work

Delta service. Hot legs to x1 & x3. Wye x2 to neutral conductor( common?, service?) x1 or x3 depending on you did the windings( alley cat bad dog)

Pootnaigle
06-17-2008, 09:04 PM
Regardless of how you mark your phase rotation Everbody needs to be on the same page when rotating the stuff!!!!!!!!!!!! I was always taught that when rotating say a 3 phase svc with a hi leg that the proper way to do it was Use the red lead of the rotation meter on the hi leg. We once ran into a problem when a neighboring crew assisted us during a conversion. Seems they Used the white lead on the hi leg. Needless to say this caused massive problems when puting everything back together. Not only was the rotation wrong but the hi leg would be on a lighting leg ,,,, smoking a few customer appliances. Lord help a guy trying to phase sumpin together hot after having used 2 seperate procedures to rotate it.

Pootnaigle
06-17-2008, 09:12 PM
Regardless of how you mark your phase rotation Everbody needs to be on the same page when rotating the stuff!!!!!!!!!!!! I was always taught that when rotating say a 3 phase svc with a hi leg that the proper way to do it was Use the red lead of the rotation meter on the hi leg. We once ran into a problem when a neighboring crew assisted us during a conversion. Seems they Used the white lead on the hi leg. Needless to say this caused massive problems when puting everything back together. Not only was the rotation wrong but the hi leg would be on a lighting leg ,,,, smoking a few customer appliances. Lord help a guy trying to phase sumpin together hot after having used 2 seperate procedures to rotate it.

lewy
06-17-2008, 09:56 PM
when ever we take a rotation we will mark X1 X2 X3 RWB(for 3 phase pad mounts) or whatever & then right down clockwise or counter clockwise then when we recheck hook up the rotation meter the same & confirm the same rotation.
I am not sure what you mean by the hi leg? Even if the red lead was on the hi leg & the other 2 were opposite the rotation would be different.
If I was checking at an overhead service I would just tape the 3 wires RWB if not already marked & hook up the matching colours on the meter & note the direction.
Again if the rotation was wrong you can change any 2 legs at the transformer.

Trbl639
06-17-2008, 10:58 PM
when ever we take a rotation we will mark X1 X2 X3 RWB(for 3 phase pad mounts) or whatever & then right down clockwise or counter clockwise then when we recheck hook up the rotation meter the same & confirm the same rotation.
I am not sure what you mean by the hi leg? Even if the red lead was on the hi leg & the other 2 were opposite the rotation would be different.
If I was checking at an overhead service I would just tape the 3 wires RWB if not already marked & hook up the matching colours on the meter & note the direction.
Again if the rotation was wrong you can change any 2 legs at the transformer.

Lewy..
on a 120/240 delta service/bank.......the hi leg/wild leg/bastard leg is the 3rd phase which the voltage usually runs 240v phase to grd..........or as some say, it'll be between 180-210volts phase to ground........it's the leg that excites the 3 phase motors!!!




on rotation............

not all rotation meters have the dot which runs clockwise or counterclockwise, and has red/white/blue leads............some are smaler, and have only 2 leads, and the 3rd one has a pin and a round handle...like a test probe.......and has 2 sets of LED lights...marked 1-2-3 or 3-2-1......and your leads are marked 1-2 (the probe) & 3.........the LED's light up to tell you the rotation................here, we are responsible for determining the rotation, when we build a bank.........................we usually mark the nside of the meter can with the rotation, something like this.........

Rotation.....

Connected..L to R......1-2-3
Reads....1-2-3
6/17/08...jb

always change the rotation by swapping any 2 of the hot legs.leaving the wild leg alone!!!! but it can also be changed on the high side of the transformers, but is rarely done that way........

what I was referring to with the color coding using 1 mark..2 marks & 3 marks, is the way we do it in this neck of the woods........if the electrician has the loop marked that way, we know exactly which phase is the wild leg............ without having to do a lot of looking to verify his colors..these idiots around here are not real bright when it comes to 3 phase:( I had one the other day, telling me we had a wild leg on a Y bank!!!!!!!!! He was in a cross-tie mill, which has 2 different services coming in to it from 2 different sides...south side (old part of the bldg) has a 120/240v service........the new part has 277/480V.....he was lost!!!!!! Checked voltage in one panel(with the wild leg) and didn't knw he was in the wrong panel!!!!!!

BTW........that hook-up is legal, because there is a firewall seperating the bldg, and the different services don't cross the firewall.....

lewy
06-18-2008, 06:26 PM
OK I have heard of it called the wild phase, learn new terms all the time here.
never heard of it as the phase that excites a 3 phase motor, just thought of it as a one of the wierd things that happens when you hook up a 240 delta with a a lighting service, 210 volts phase to ground from the leg that is not part of the 120/240 service.
I agree that if your rotation was wrong you would change the other 2 just a whole lot easier.
As far as the general subject of phase rotation on new connections the electrician is responsible for his own, where I come from. Obviously on reconnects we have to keep it the same & that is why your rotation meter has to be hooked with all 3 leads the same as the original check.