Bank ?

[halfhitch]

In a banking class a few years back, the instructor talked about a bank where a leading phase must apply. (A leads B. B leads C. C leads A.) is there anyone here that can explain this in detail? And is there a website that explaines tranformer banking?

[Edge]

you need to look at your phasor diagram see if the bank is built 0degrees 180....etc... think think a triangle... it helps... if your building an up right triangle vs a downward one then your phases swap on the secondary side... don't just look at the print look at the phasor diagram... then you will see how one phase can lead another...

and no Swimpy I'm not talking about klingons...

I'm tired as hell atm so sorry if that makes no sence... I'll try to get back to you tomorrow evening with something that might...

damn it man another post for 'door...

Edge

[ratbastard101]

In a banking class a few years back, the instructor talked about a bank where a leading phase must apply. (A leads B. B leads C. C leads A.) is there anyone here that can explain this in detail? And is there a website that explaines tranformer banking?

Primary, just like secondary, is either clockwise or counter clockwise rotation. Our system is Clockwise. In a clockwise rotation A leads B, B leads C, and C leads A. Think of what 60 hertz looks like on a ocilliscope. The voltage is constantly going up and down.

Take that mental picture and add another phase to the ociliscope (if its a wye system it will be 120 degrees out from the first phase.) If A phase is at 0 degrees then B would be at 120. Now add a 3rd phase at 120 degrees past B phase (240 degrees).

IF you labeled each phase as it peaks on the ocilliscope then you would see this

A B C A B C A B C A B C and so on

Now looking at it you see how A phase peaks before (leads) B phase and so on.

This matters on a Transfomer Bank due to the order in which secondary phase peaks (or leads) another is in direct relation to which primary phase is feeding the transformer the secondary comes from.

This is important to understand as well when balancing load on a circuit by swapping phases on laterals and stuff because you could end up swapping the rotaion of a transformer bank and causing damage to customers equipment.

If you know the rotaion of your system, for instance A leads B, B leads C and C leads A then you will never have a problem as long as you keep that order.

So in short if A leads B and B leads C and C leads A then you have a clockwise rotation. If you have a lateral on A and C phase and you need to move load off of A phase then you should put the phase that was fed by C phase to B phase and the phase that was on A gets moved to C. This will ensure that any 2 pot banks stay the same.

This is the way I understand all of this anyhow. I am sure if I was misinformed that someone will correct me. :D

[BigClive]

In a banking class a few years back, the instructor talked about a bank where a leading phase must apply. (A leads B. B leads C. C leads A.) is there anyone here that can explain this in detail? And is there a website that explaines tranformer banking?

That sounds like an odd description of phase rotation. It's not so much one particular phase leading the others, it's the way the current "rotates" around them. Is this what you're talking about?

If it is phase rotation then it's most important to observe when changing the supply to a factory or other premises with a lot of three phase motors, since it will affect the direction they run. With modern machines containing electronic motor drives the rotation is sometimes not important since they generally rectify the mains to DC then recreate their own three phase output.

[T-Man]

It hard to explain things like phase rotation in a forum like this, so I took a page out of another site that has been passed around in these forums before. Take a look at this page and see if it answers your question.

http://www.allaboutcircuits.com/vol_2/chpt_10/3.html

This is what the others were trying to get across to you I think. . .
Good question though.

[lewy]

Up here we try to keep it simple, on new instalations any thing over 150 kva is a pad mount & the electrician has to make the connections with his wire , on the overhead we make the connections for them, rotation is there responsibility. I agree with an earlier post rotation can only be clockwise or counter clockwise. We always check rotation before we disconnect & confirm after we reconnect if the rotation is wrong we would just change the connections on any 2 of the secondary leads. If we have to balance load we would just feed transformers off of different phases, we would not be changing the phase on the primary side because most of our system is a loop, we might on single phase radial runoffs only.

[BigClive]

Secondary voltage phase rotation indicators are cheap and readily available. I just thought I'd mention that.

[Fiberglass Cowboy]

Like Clive just said about rotation meters. Readily available. The important thing to remember when checking phase rotation with any style of secondary phase rotation meter (there are many various types); is to use the same meter when disconnecting or reconnecting anything. Phasing and polarity apply to all transformer banks, though we do not worry about any of this on new construction, much like Lewy said. Only on replacements/rebuilds. Though I understand what your instructor was saying, not sure why he wouldn't put it to you in simpler terms.:confused:

Later gator, don't be a player hater...... "Ed" :cool:

[Edge]

thought about this to day... I think he was talking about leading and lagging banks...

has to do mainly with open banks where you have a lighting pot and a power pot... one phase "leads" the other...

I'm to damned tired to write half the shit I was thinking so I'll leave it at that... but Clive can prolly expond on the shit about the sine waves and shit and how when their balanced they are "in phase"...

If no one gets back on this idea of mine... I'll see if I can fluff it up for ya tomorrow...

Edge

[ratbastard101]

It hard to explain things like phase rotation in a forum like this, so I took a page out of another site that has been passed around in these forums before. Take a look at this page and see if it answers your question.

http://www.allaboutcircuits.com/vol_2/chpt_10/3.html

This is what the others were trying to get across to you I think. . .
Good question though.

http://www.allaboutcircuits.com/vol_2/chpt_10/3.html

Like they say a picture is worth a thousand words. The picture showing 3 phases and their respective sine waves was what I was trying to put into words. As long as you keep the phases in the correct order (wye only) it does not matter.

On a two pot bank one transformer "leads the other" since one primary phase leads the other. I am unsure if it actually matters which is leading which as long as during any retrofit or rebuild that relationship stays the same.

[Edge]

good to see ya back 'door...

Edge

[Brooks]

In a banking class a few years back, the instructor talked about a bank where a leading phase must apply. (A leads B. B leads C. C leads A.) is there anyone here that can explain this in detail? And is there a website that explaines tranformer banking?

I’m not sure if this is what the OP was referring to but it fits;

This is what I was taught. We used to do this all of the time. These days you are lucky to find anyone that remembers… Well I digress!

I believe your instructor was referring to and Open Wye Open Delta; The lighting pot (or larger pot) should be on the leading phase. It has to do with imbalance and inefficiencies in Open Wye-Delta banks. Think about it a bit and it will come to you! ;)

To determine if you built the bank correctly, maps are correct, blah blah blah! :)

Mark the high leg blue for “C” phase. You might throw some orange tape on it as well. This marking will not change and was once industry standard…

Then;
Put the “C” phase lead from your rotation meter on the high leg.
Put the “B” phase lead from your rotation meter on the leg tying the x1 and x3 of the two pots.
Put the “A” phase lead from your rotation meter on the last leg (single on the lighting pot).

If you get clockwise rotation, the lighting pot is on the leading phase. If not, you can rearrange the secondaries, swap primaries... Well, I won't tell you how to do your work, just how to do it right! :D

[Edge]

Damn Brooks thats it... shit I forgot about this thread...

like you said hook it up and it's clock... it's leading... hook it up opposite with the rotation meter the same way then it's laggin...

yessir! thats the fuggin answer to the mans question... and thanks for dust out the cobwebs in my skidlid!

Edge