208/120V system 2-pole load a 2 phase or single phase?

A 208Y/120V, 4 wire system has some loads with 3-pole CB which are 3 phase, 1 pole CB which are single phase. But what about the 2-pole CB loads, are these considered 2ph loads or single loads? which formula is applicable in this case: current= kW/(208V) or current=kW/(208*sqrt(2)*pf)? thnaks
 

DrSparks

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Location
Madison, WI, USA
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A 208Y/120V, 4 wire system has some loads with 3-pole CB which are 3 phase, 1 pole CB which are single phase. But what about the 2-pole CB loads, are these considered 2ph loads or single loads? which formula is applicable in this case: current= kW/(208V) or current=kW/(208*sqrt(2)*pf)? thnaks
Yes they are single phase loads. And it's sqrt(3) not 2. You don't need that in your calculations for 1ph.

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DrSparks

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Location
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the voltage is line-to-line plus neutral. I would consider it 2-phase, thus, the formula to apply is the 2-ph formula (voltage line to line, sqrt (2)). why is that consider single phase?

View attachment 2557426
It's not 2 phase. What device are you connecting that requires 2 phase and a neutral? Electric ranges and dryers require them but that's a multi wire branch circuit (MWBC). The internal circuits that are made inside the appliance are all single phase. For example: line to line for high setting on a burner... single phase. Line to neutral for the computer power supply... line to neutral... etc.

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DrSparks

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To put it simply, you are using two phases of a 3 phase system. The phases are still 120 degrees out of phase. A 2 phase system has it's phases 90 degrees out of phase.

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DrSparks

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I'm glad that we don't have this complexity in UK and Europe.........................:)
Are you saying you do not use 3 phase power in the UK? I find that highly unlikely my good friend.

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Besoeker3

Senior Member
Location
UK
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Electrical Engineer
Are you saying you do not use 3 phase power in the UK? I find that highly unlikely my good friend.

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Not at all. My comment was about the 208V and the 120V.
We just have 230V single phase and 400V three phase.
 

don_resqcapt19

Moderator
Staff member
Location
Illinois
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retired electrician
the voltage is line-to-line plus neutral. I would consider it 2-phase, thus, the formula to apply is the 2-ph formula (voltage line to line, sqrt (2)). why is that consider single phase?

View attachment 2557426
The load is supplied by a single winding in the generator, the A - B winding, making it a single phase. The load needs to be supplied by multiple windings to make it something other than single phase.
 

Jraef

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Staff member
Location
San Francisco Bay Area, CA, USA
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Electrical Engineer
the voltage is line-to-line plus neutral. I would consider it 2-phase, thus, the formula to apply is the 2-ph formula (voltage line to line, sqrt (2)). why is that consider single phase?

View attachment 2557426
Although now very rare, "2-phase" is a real thing, but not what you show there.

epst-3e_14_17.jpg


However if you are from Europe, they call what you showed "2-phase", which can be confusing to those of us in North America, where we really do have it. We call it single phase.
 

gar

Senior Member
210802-2010 EDT

Two hots and one neutral from a 3 phase system are a 2 phase source. Any 2 wires from this source are a single phase source.

As soon as any source has more than two wires, then it has the possibility of being a multiple phase source.

.
 

DrSparks

The Everlasting Know-it-all!
Location
Madison, WI, USA
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Master Electrician and General Contractor
The load is supplied by a single winding in the generator, the A - B winding, making it a single phase. The load needs to be supplied by multiple windings to make it something other than single phase.
Or a single coil in a transformer

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jim dungar

Moderator
Staff member
Location
Wisconsin
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Retired Electrical Engineer - Power Systems
To put it simply, you are using two phases of a 3 phase system.
You are using 2 phase conductors.

I believe a source of confusion is caused by people using the simple word 'phase' as a noun instead of as an adjective.
 

DrSparks

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Location
Madison, WI, USA
Occupation
Master Electrician and General Contractor
210802-2010 EDT

Two hots and one neutral from a 3 phase system are a 2 phase source. Any 2 wires from this source are a single phase source.

As soon as any source has more than two wires, then it has the possibility of being a multiple phase source.

.
What publication are you referring to? Again, what device in a home, commercial establishment, or modern industry would utilize 2 phase current?

If you use 2 phases of a 3 phases system and hook it up to a scope, just how many sine waves are you going to see, hmm?

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DrSparks

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Location
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You are using 2 phase conductors.

I believe a source of confusion is caused by people using the simple word 'phase' as a noun instead of as an adjective.
Phase is a noun.

It is used to refer to a conductor carrying the phase current of a polyphase system. It could also refer to the phase of current or voltage in a formula. Either way it's a noun.

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DrSparks

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Location
Madison, WI, USA
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Master Electrician and General Contractor
Not when it is used to describe a single conductor as in 'for a 2 wire circuit you need to pull a phase and neutral'.
Of course it is.

If you said, for example, you need to pull a blue phase, then blue would be the adjective and phase would be the noun.

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gar

Senior Member
210802-2051 EDT

DrSparks:

Take a two channel scope ( supply it from an isolation transformer to avoid a grounding problem thru the scope ) and connect the scope chassis to the power system neutral wire for the electrical reference point.

Connect channel A scope probe to one of the hot phase conductors. Get scope sync from channel A. Connect channel B to the second phase conductor.

Displayed on the scope are two sine waves with a phase difference between them of about 120 degrees.

.
 
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