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"Single Phase"" From a WYE

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gar

Senior Member
Location
Ann Arbor, Michigan
Occupation
EE
230624-159 EDT

In our area we have many open deltas. At the building where my son has his shop he is supplied with an open delta as are about 5 other businesses, all from two transformers. His load is lighting, about 5 CNC machines, a 40" wide belt sander, chop saw, two bandsaws, welders, furnaces, and two air conditioners..

From two phases of a 3 phase wye source you can create three phase with additional windings on the two transformers or with added transformers.

From a single phase center tapped transformer, two phases, you can not generate a 3 phase output with just ordinary transformers.

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GoldDigger

Moderator
Staff member
Location
Placerville, CA, USA
Occupation
Retired PV System Designer
I would call it "two out of three phase 120 wye". Often in apartment houses or other multiple occupancy situations the service is wye and each unit gets two out of three for 208/120 volts using a standard "single phase" panel. Which two are used is spread over the units in the building to best balance the phase loading.
 

jim dungar

Moderator
Staff member
Location
Wisconsin
Occupation
PE (Retired) - Power Systems
I would call it "two out of three phase 120 wye". Often in apartment houses or other multiple occupancy situations the service is wye and each unit gets two out of three for 208/120 volts using a standard "single phase" panel. Which two are used is spread over the units in the building to best balance the phase loading.
The source and usually the utility setvice drop that supplies the voltage is 3-phase 4-wire.
Your unit's supply/circuit is only 3-wires, 2 lines and 1 neutral, so the way I was tought this is single phase because there is only 1 Line-Line voltage.

This type of system is very common in apartment building, such that it is a standard offer in multi-meter centers. My area utilities called this a 'network' service.
 

jaggedben

Senior Member
Location
Northern California
Occupation
Solar and Energy Storage Installer
For what it's worth I've heard some utilities call it Single Phase 120/208. As far as 'does it have a name' that's probably the best you can do.

Actually teaching the kids to understand it requires more than a name anyway.
 

don_resqcapt19

Moderator
Staff member
Location
Illinois
Occupation
retired electrician
For what it's worth I've heard some utilities call it Single Phase 120/208. As far as 'does it have a name' that's probably the best you can do.

Actually teaching the kids to understand it requires more than a name anyway.
Per IEEE, when the lower voltage is shown first, it is single phase and when the higher voltage is shown first it is 3 phase.
 

Joethemechanic

Senior Member
Location
Hazleton Pa
Occupation
Electro-Mechanical Technician. Industrial machinery
120-30-30.jpg

I was just hoping there was a name for it I could tell them to google so they could read or watch videos or whatever they want to do. It would save trying to explain it to these guys one by one. It ain't like I've got them all together in a classroom
 

mtnelect

HVAC & Electrical Contractor
Location
Southern California
Occupation
Contractor, C10 & C20 - Semi Retired
Still not sure what that has to do with a single vs 3 phase thread

When @Joethemechanic mentioned; Even if your 120 single phase loads are perfectly balanced you will have a neutral current. For me, it triggered my reference to current flow on the neutral(s) and my assertion that this is why there are so many problems with GFCI. And all neutral(s) in general. I guess, I am stuck on neutral !
 

don_resqcapt19

Moderator
Staff member
Location
Illinois
Occupation
retired electrician
When @Joethemechanic mentioned; Even if your 120 single phase loads are perfectly balanced you will have a neutral current. For me, it triggered my reference to current flow on the neutral(s) and my assertion that this is why there are so many problems with GFCI. And all neutral(s) in general. I guess, I am stuck on neutral !
What problems are you talking about.
 

Joethemechanic

Senior Member
Location
Hazleton Pa
Occupation
Electro-Mechanical Technician. Industrial machinery
I actually went out one time to look at a 3 phase radiac chop saw that tripped the overloads whenever they tried to cut anything heavy. High leg delta service. Back at the panel the branch circuit was connected to B, C and neutral. Opening that panel and seeing a 2 pole breaker for a 3 phase load had me going WTF for a minute
 

Joethemechanic

Senior Member
Location
Hazleton Pa
Occupation
Electro-Mechanical Technician. Industrial machinery
This thread is starting to remind of that time at church when I said Adam must have had free will before the fall because God allowed him to name the animals
 

tortuga

Code Historian
Location
Oregon
Occupation
Electrical Design
At work we always called that 208/120 open-wye.
I definitely correct people whom call it 2-phase becasue there is a 3-wire two phase (90 deg).
It would be a good lesson on apparent power vs real power.
 

winnie

Senior Member
Location
Springfield, MA, USA
Occupation
Electric motor research
Back in January I proposed 'psingle phase' as the name for this system, but I don't think the term has caught on :) :)

 
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