240 split phase. Are you correct or not?

[timselectric]

Not really.
It's fairly simple, once you see it.
My work is done, here.
I believe, with enough time to think about it.
Everyone can eventually understand.

 

[tigerwillow1]

My work is done, here.

Sigh, if your work wasn't done I would have asked why it's wrong to call split-phase power 2-phase, and yet call 6-phase power 6-phase. Maybe somebody else with a greater understanding than I can explain it. For starters here are some random Internet excuses to not call it 2 phase:

- This is called split phase because there is more than one voltage from a single transformer.
- Since the two phasors do not define a unique direction of rotation for a revolving magnetic field, a split single-phase is not a two-phase system.
- It’s a religious phenomenon.
- Single phase means that the AC power is delivered by one pair of wires.
- Even if you have a disturbance on the “high tension” line…. you still get a mirror image on the L1 and L2 split-phase.
- A two phase motor is used for servos.
- Two phase is where the two phases are 45 degrees apart if my memory serves me well.
- The only two phase system I have come across was 120°.
- Our utility references the 120v/240v service coming to the residence as a single phase service.
- The term “split-phase” merely refers to the split-voltage supply in such a system.

But then I still can't figure out why a 6-phase feed isn't called something like triple split phase instead .

 

[Spunky]

If it looks like 2-phase to you, you don't understand what you are looking at. There's only a single phase.
This comes from the misunderstanding of 3-phase.
Some people are under the impression that each of the 3 wires are a phase. When it's actually the combination of 2 legs that make a phase.
3-phase
1 & 2 = phase A
2 & 3 = phase B
3 & 1 = phase C

Single phase
1 & 2 = one phase

Split-phase
1 & 1.5 & 2 = one phase , split in half.

That is probably true where it is being generated (a Delta system), but if the substation is supplying through Wye transformers, it would be a phase to ground voltage.
So, again... it's relative to your perspective. LOL

 

[timselectric]

That is probably true where it is being generated (a Delta system), but if the substation is supplying through Wye transformers, it would be a phase to ground voltage.
So, again... it's relative to your perspective. LOL

This is part of the misconception. It's not a phase to ground. It's a single leg to ground. A leg, that is common to two different phases. But, just a leg.

 

[Spunky]

This is part of the misconception. It's not a phase to ground. It's a single leg to ground. A leg, that is common to two different phases. But, just a leg.

So, a lone inverter can not by it's self make a phase?

 

[timselectric]

So, a lone inverter can not by it's self make a phase?

Sure it can.
A single phase
Some can make 3 phase too

 

[Spunky]

View attachment 125150

The high side of the above transformers are wired in a wye configuration and will function independently and absent either or both of the other two phases.

What would be the difference between the terms 'leg' and 'phase' here?

 

[timselectric]

The high side of the above transformers are wired in a wye configuration and will function independently and absent either or both of the other two phases.

What would be the difference between the terms 'leg' and 'phase' here?

It takes two legs to make a phase.

When wired in a wye configuration.
A to B is a phase.
B to C is a phase.
C to A is a phase.
A,B, or C to common is half (actually a little more than half, because of the phase angles) of a phase. (In respect to the 3 phases)

 

[Nobodybusiness]

Not really.
It's fairly simple, once you see it.
My work is done, here.
I believe, with enough time to think about it.
Everyone can eventually understand.

Looks interesting to me.

You all are still talking about it.

 

[42OhmsPA]

Seems like there are and always will be lots of split opinions, it's a never ending phase.
My rookie understanding is you can't have split phase without a neutral. Would that be correct?

 

[Mattb4]

So, a lone inverter can not by it's self make a phase?

Being able to use the outputs of two HF inverters nowadays to create a 120/240v feed is pretty nifty. Bit beyond me how each inverter syncs up to product the 180 out of phase outputs. Electronic magic.

 

[Checkthisout]

If it's "2 phases 180 degrees out", and 3 phase is 120 degrees out, how am I able to get "2 phase" out of a 3 phase transformer?

The peaks wouldn't line up at 120 and 180

I think it only works if we have 1 phase.

 

[Checkthisout]

Not really.
It's fairly simple, once you see it.
My work is done, here.
I believe, with enough time to think about it.
Everyone can eventually understand.

Your years of experience have hardened you.

Nothing phases you anymore.

 

[Spunky]

If it's "2 phases 180 degrees out", and 3 phase is 120 degrees out, how am I able to get "2 phase" out of a 3 phase transformer?

The peaks wouldn't line up at 120 and 180

I think it only works if we have 1 phase.

I guess you are kind of on to where my thought is coming from.

If you were referencing a 120v phase to another phase of three (120 degrees out), you would see 208v (120*√3), but 120v to a system neutral in a Wye system.

In a Delta system (has no neutral or reference to ground), if one of the three phases are lost, it's said that you would now have only single phase available. Either system needs a return path to function.

The pad-mounted 3∅ transformers I work with all have three separate transformers wired inside the oil filled case. Just like you'd see 3 overhead transformers clustered together on a pole. In this Wye transformer, if a phase is lost up stream (even at the sub station), you will still get 120v to the neutral on each of the remaining phases and 208v across the two phases.

The reality is that three phases were created simultaneously at the generation plant and never existed individually (as it was designed and wouldn't work if it lost a phase there). In a solar field, the individual phases are created separately and would be usable, even if the other two phases were absent.

Or am I missing some basic thought here?

 

[Mike 134]

To summarize real electricians know it's split phase, all the handymen will have various names for it.

 

[timselectric]

Seems like there are and always will be lots of split opinions, it's a never ending phase.
My rookie understanding is you can't have split phase without a neutral. Would that be correct?

Not exactly. The center tap (halfway across the single phase), makes it split-phase. In most cases this conductor is also bonded to ground ( AKA, a neutral). But it doesn't have to be, for a split-phase configuration.

 

[timselectric]

If it's "2 phases 180 degrees out", and 3 phase is 120 degrees out, how am I able to get "2 phase" out of a 3 phase transformer?

The peaks wouldn't line up at 120 and 180

I think it only works if we have 1 phase.

3 phase requires 3 legs. If you lose one, you are left with only 2 legs. Two legs gives you single phase.
The reason 3 phase is used is because it's cost effective. Just by adding one more conductor, you can carry 3 x as much power.
A sign wave travels through 360 degrees, from peak to peak. 3 equally spaced (timed) sign waves are 120 degrees from each other.
Single phase power flows in one wave.
Think of split-phase as two people riding a tandem bicycle.
As they pass by you, for a split second. It would appear that one person (front seat) is traveling away from you. And the other person (back seat) is traveling towards you. But they are both traveling in the same direction.
The point of reference can change what you see. But it doesn't change what is actually happening.

 

[Checkthisout]

3 phase requires 3 legs. If you lose one, you are left with only 2 legs. Two legs gives you single phase.
The reason 3 phase is used is because it's cost effective. Just by adding one more conductor, you can carry 3 x as much power.
A sign wave travels through 360 degrees, from peak to peak. 3 equally spaced (timed) sign waves are 120 degrees from each other.
Single phase power flows in one wave.
Think of split-phase as two people riding a tandem bicycle.
As they pass by you, for a split second. It would appear that one person (front seat) is traveling away from you. And the other person (back seat) is traveling towards you. But they are both traveling in the same direction.
The point of reference can change what you see. But it doesn't change what is actually happening.

Agreed. I think people might be confused because the time function is the same.

Split phase 120 sine waves overlay the 240V waves its just that the waves aren't as tall because the voltage is less due to only using 1/2 of the transformer.

I like this graphic.

 

[timselectric]

I guess you are kind of on to where my thought is coming from.

If you were referencing a 120v phase to another phase of three (120 degrees out), you would see 208v (120*√3), but 120v to a system neutral in a Wye system.

In a Delta system (has no neutral or reference to ground), if one of the three phases are lost, it's said that you would now have only single phase available. Either system needs a return path to function.

The pad-mounted 3∅ transformers I work with all have three separate transformers wired inside the oil filled case. Just like you'd see 3 overhead transformers clustered together on a pole. In this Wye transformer, if a phase is lost up stream (even at the sub station), you will still get 120v to the neutral on each of the remaining phases and 208v across the two phases.

The reality is that three phases were created simultaneously at the generation plant and never existed individually (as it was designed and wouldn't work if it lost a phase there). In a solar field, the individual phases are created separately and would be usable, even if the other two phases were absent.

Or am I missing some basic thought here?

You are very close.
It doesn't really matter if the 3 phases were created simultaneously by a single generation or individually and synchronized together. Whatever is electrically conducted to the end is available.
The reason that 3 separate transformers are used. Is because of its reliability. If a single transformer fails (open delta or wye), the remaining 2 can still provide the 3 phases. They are sized to carry the increased current. But the loads need to be fairly balanced, or it would overload one of the remaining transformers.
This configuration allows power to continue flowing, until the 3rd transformer can be replaced. And even allows it to be swapped without customer down time.
This only applies to individually cased transformers.

Both Delta and Wye systems can be grounded or ungrounded.
As long as there's a complete circuit path, current will flow.

 

[timselectric]

Agreed. I think people might be confused because the time function is the same.

Split phase 120 sine waves overlay the 240V waves its just that the waves aren't as tall because the voltage is less due to only using 1/2 of the transformer.

I like this graphic.

View attachment 125209

If you change the 240v labels to 120v, and remove the 120v labels. And remove the red and blue waves. Then you would be accurately displaying split-phase configuration. There is only one phase.