3 cans on a pole

[Fred B]

Not real familiar with 3ph and how utility is deriving it. I know from the book the the basics of 3ph, but seeing actual product with hands on limited. From what is seen here what can I expect inside the building? I know its is 3ph, but why 3 cans? Any way to know if I'm seeing a delta or wye? It looks like they only grab 1 leg of potential 2 on each can, any thing seen here can tell me voltages I may find inside? I know there is some 120V from other similar sites I've worked in. Curious as to the outside service.
Thank you for educating me.

 

[Greentagger]

It appears that it may be 3 ph 120/208. Usually you can tell if there is gonna be a high leg, because one of the transformers is usually smaller in size than the other 2.

Guess it could also be 277/480.

 

[Hv&Lv]

not an extremely clear picture, but appears to be an ungrounded wye/delta.

basically a three pot high leg bank
look at the one transformer with no center connection. That entire coil is now used rather than being center tapped.

you should see 120/240 three phase with a high leg of 208-216 volts, depending on the 120 base voltage. (ie., 125V will be 216.5V high leg).

it would be much easier to tell with a picture of one other transformer secondary on the bank.

 

[Hv&Lv]

It appears that it may be 3 ph 120/208. Usually you can tell if there is gonna be a high leg, because one of the transformers is usually smaller in size than the other 2.

Guess it could also be 277/480.

when a transformer is used for 120/208 the guys in the field have to reconfigure the internal coils to parallel with one side being grounded, the other side is connected to the phase.
also on a 120/208 bank the XFs are one phase, one pot. Meaning there isn’t a wire going from one secondary bushing to another.
Like this..

 

[hillbilly1]

It appears that it may be 3 ph 120/208. Usually you can tell if there is gonna be a high leg, because one of the transformers is usually smaller in size than the other 2.

Guess it could also be 277/480.

All of the deltas I’ve seen, one can is larger than the other two. Majority of the load is single phase.

 

[Terminator5047]

Not real familiar with 3ph and how utility is deriving it. I know from the book the the basics of 3ph, but seeing actual product with hands on limited. From what is seen here what can I expect inside the building? I know its is 3ph, but why 3 cans? Any way to know if I'm seeing a delta or wye? It looks like they only grab 1 leg of potential 2 on each can, any thing seen here can tell me voltages I may find inside? I know there is some 120V from other similar sites I've worked in. Curious as to the outside service.
Thank you for educating me.
View attachment 2557323

3 cans because that way the can physically hang it in a pole and it’s more universal that way they can easily do different configurations

 

[hillbilly1]

Here is a typical delta. Gotta figure out why the site keeps flipping pictures sideways!

 

[Fred B]

Is it truely only deriving 1ph from each can as it looks like? Or is there likely a transformer inside? The cans look the same as what I find on the 120/240 residential I do most of the time. But the secondary only utilizing 2 of 3 taps.

not an extremely clear picture, but appears to be an ungrounded wye/delta.

So I should or would not find a grounding conductor coming down the pole, correct?

basically a three pot high leg bank
look at the one transformer with no center connection. That entire coil is now used rather than being center tapped.

you should see 120/240 three phase with a high leg of 208-216 volts, depending on the 120 base voltage. (ie., 125V will be 216.5V high leg).

So the pole configuration here I should find on center phase in panel higher voltage to neutral than the other 2 if it has a wild leg?
I just think it is nice to know as I approach a job possible hazards, ie wild leg.

it would be much easier to tell with a picture of one other transformer secondary on the bank.

Didn't really have access for a walk around and pic took from some distance.

 

[Hv&Lv]

All of the deltas I’ve seen, one can is larger than the other two. Majority of the load is single phase.

I have built many deltas with all same size XFs over the years

 

[Hv&Lv]

Here is a typical delta. Gotta figure out why the site keeps flipping pictures sideways!

And if you look at the XF on the left it has the center X0 bushing ungrounded

 

[Hv&Lv]

Is it truely only deriving 1ph from each can as it looks like? Or is there likely a transformer inside? The cans look the same as what I find on the 120/240 residential I do most of the time. But the secondary only utilizing 2 of 3 taps.

So I should or would not find a grounding conductor coming down the pole, correct?

So the pole configuration here I should find on center phase in panel higher voltage to neutral than the other 2 if it has a wild leg?
I just think it is nice to know as I approach a job possible hazards, ie wild leg.

Didn't really have access for a walk around and pic took from some distance.

Take a look at the pic in post 3. Notice the secondary side. The coils are tied together. A delta takes the voltage at the “corner” of the coils.
This one has one XF center tapped at the X0 bushing. There will be a grounded conductor coming also.

This configuration should show a high leg in the center of the panel with a VOM.
always poke around with a VOM first and compare the readings with experiential knowledge of what seems normal.

 

[hillbilly1]

I have built many deltas with all same size XFs over the years

Yes, but have you built any with one can smaller though? That’s my point.

 

[hillbilly1]

And if you look at the XF on the left it has the center X0 bushing ungrounded

Yes, the center larger can has the center bushing grounded and is the neutral.

 

[Dsg319]

Check these guys out on YouTube, they easily explain all kind of different transformer bank configurations.