Static add a phase

Thread Starter

300-3056

Joined Sep 9, 2022
26
Hello:
First time poster long time reader....

I am an electrician with some college ( long time ago I might add ).
Recently I was asked to solve a simple problem convert some three phase equipment to single phase power.
The simpler solution is use whats called a rotary phase convert or a static converter.
One makes imbalanced but good enough power using a repurposed induction motor and the other using capacitance to start an three phase motor only.

In thinking this out searching for a circuit I once saw that used both a transformer and motor I discovered something I have never seen before a static converter that uses a transformer for phase shifting to create three phase power from a single phase source.
I can't wrap my head around it I don't understand how you can make three power from a single transformer.
So here are a couple links I have that might help explain what I am seeing and a little math to back up how this might work would be appreciated.

One here is a link to some technical papers and there is a IEEE reference to something in fig #5 that looks like SOLA transformer.
It not clear to me how that might be adapted to make 3 phase power.
This would operate in the saturated region and would burn off a lot of power just as heat.
( Not a very good converter if I understand what I am seeing )
A lot of what I have read here is just a touch over my head and what I do understand all seems to operate in the saturated region of the iron, and often requires electronics.
Non of this helps me.....
But I guess its a starting point

https://www.researchgate.net/public...AN_OPTION_TO_RURAL_ELECTRIFICATION_-_A_REVIEW

I see this video and I am thinking inductive phase converter, that's using a more lagging power factor on one leg to create an imbalanced three phase output.
I could see this having some advantages.
He also says it has capacitors so that could be useful for some lead on another leg ( and start capacitors, he says that too )
Under high load starting maybe the inductance is high enough to also act as a reduced voltage starter
Not the best way to reduce inrush current but if your not paying for power factor in a residential setting maybe its practical is a link to this strange transformer ( but no description of how its connected, it looks very crude and leaky maybe that's part of how it works ?like a saturable core in a welder ? )


Any theories or opinions are welcome
Its not really an important thing, I just would like to understand the video and what this could be I am seeing.
And if anyone has a copy of electrical machines drives and power systems I would love to see that the author used in his home shop again so I could copy that particular converter with the motor and auto transformer connection.
Thank you
 
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nsaspook

Joined Aug 27, 2009
10,410
A proper 3-phase inverter using modern technology is a no brainier compared to inefficiently faking 3-phase with inductive components. We use 3-phase motor-generator rotary sets to isolate utility power from hi-voltage potentials where the common and grounds of circuits and power distribution are up to 500KV above earth ground. It works but is expensive.
 
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Thread Starter

300-3056

Joined Sep 9, 2022
26
A proper 3-phase inverter using modern technology is a no brainier compared to inefficiently faking 3-phase with inductive components. We use 3-phase motor-generator rotary sets to isolate utility power from hi-voltage potentials where the common and grounds of circuits and power distribution are up to 500KV above earth ground. It works but is expensive.
Yes I am aware of these things.
I even work on some of them, but what I am really interested in is the transformer action in that static phase converter.
Professional curiosity more than anything.
The task at hand of making a simple "Add- a-Phase" and installing it is a no brainer, also simpler and and cheaper than buying some electronics.

Thank you for the reply, but I really want to know what that home made transformer is doing and how one can make a meaningful phase shift network with it as appears in the Youtube video.

 

nsaspook

Joined Aug 27, 2009
10,410
Think about it. If "Add- a-Phase" was really simpler and cheaper the bean-counters that pay the bills would be forcing (engineers who would then rewrite the specifications to require real 3-phase power) them on engineering staffs as the best deal. Those types of systems mainly run two phases of a three-phase motor with the third phase current from a Scott-T transformer. or some capacitor phase network. Those heavy duty line frequency reactive components today making 'dirty' power will be more expensive than cheap electronics switching in the several kHz to generate 3-phase power.

https://www.google.com/search?q=sco...HSNoCxUQ_AUoAnoECAIQBA&biw=1920&bih=929&dpr=1

https://www.eeeguide.com/phase-conversion-in-transformer/
 

Thread Starter

300-3056

Joined Sep 9, 2022
26
Think about it. If "Add- a-Phase" was really simpler and cheaper the bean-counters that pay the bills would be forcing (engineers who would then rewrite the specifications to require real 3-phase power) them on engineering staffs as the best deal. Those types of systems mainly run two phases of a three-phase motor with the third phase current from a Scott-T transformer. or some capacitor phase network. Those heavy duty line frequency reactive components today making 'dirty' power will be more expensive than cheap electronics switching in the several kHz to generate 3-phase power.

https://www.google.com/search?q=sco...HSNoCxUQ_AUoAnoECAIQBA&biw=1920&bih=929&dpr=1

https://www.eeeguide.com/phase-conversion-in-transformer/
Thanks I appreciate your input.
Are you an engineer?

You know if your smart about it you can put three phase into a scott T wired with two transformers and get 3 phase plus a neutral out ... Again with only two transformers, its a cheap way of doing things ( I am point the fickle finger of old fart at you Marcus transformer of Montreal... )

But I am not able to make any use of that nor does it help me understand the video.

Cheap is in the eye ( and scrap pile ) of the beholder.
I can get away with small motor like T 143 two pole.
I can be clever about it and add 10% more winding to the leg I am inducting too.
( and I can design and wind it myself.... not rocket surgery )

Again what I am asking and think about this carefully!!!!!
How does he get from that abortion of a home made transformer from the core of an old electric motor wound with machine tool wire to a better add a phase?
That's all I am trying to understand here.

Scott T is of NO help here.
I am not interested in 2 phase to 3
He's made a claim that his winding can get a static converter to induce good three phase with a big of added capacitance.
I don;t see how this is possible.
I did some google and found nothing.

Maybe he is full of fecal matter.
That's what I am trying to figure out here.

Is there any mathematical model of how one can make three phase from single phase in one shot without any weird fero resonant effects or electronics?
I cant see how it works, and I would like to understand it.
 

nsaspook

Joined Aug 27, 2009
10,410
Yes. The Scott T is obviously bidirectional (it's just magnetic flux) so it can go (real 2 phase) 2 -> 3 with two Non-Collinear Vectors using the principles of I/Q modulation.
https://www.allaboutcircuits.com/te...anding-i-q-signals-and-quadrature-modulation/
https://studylib.net/doc/18304942/the-single-phase-to-three-phase-converter-using-scott-con...

The eeguide link I posted before gives the math.
https://www.electricaltechnology.org/2022/03/scott-t-connection-transformer.html

If your willing to rig and DIY something from scrap that's fine. It's possible and was useful on the old school days to drive two-phase motors from a three-phase feed before modern electronics.
 

Thread Starter

300-3056

Joined Sep 9, 2022
26
I'm not sure you are following me.
Can you show me how in one step with a transformer only you can create any poly phase systems?
I can't think of any way

Please do not say Scoot T again its not going to work.
I have an apprentice who is a physicist ( No bull shit, job does not pay unless you do contract work for Iran I guess ).
He asks me how things work....
He helps me with the math sometimes.

Nothing here can be explained One to Three via transformer only.
There are a box full of capacitors claimed in the video, some to start some to run....

So what is going on here.
IS it BS?
is it an auto transformer or some sort of reduce voltage starter with a normal static converter?
I am starting to think that's possible.... ( but this who thing still smells funny )

Please watch the video see what I see and try to explain.
 
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nsaspook

Joined Aug 27, 2009
10,410
I'm not sure you are following me.
Can you show me how in one step with a transformer only you can create any poly phase systems?
I can't think of any way

Please do not say Scoot T again its not going to work.
I have an apprentice who is a physicist ( No bull shit, job does not pay unless you do contract work for Iran I guess ).
He asks me how things work....
He helps me with the math sometimes.

Nothing here can be explained One to Three via transformer only.
There are a box full of capacitors claimed in the video, some to start some to run....

So what is going on here.
IS it BS?
is it an auto transformer or some sort of reduce voltage starter with a normal static converter?
I am starting to think that's possible.... ( but this who thing still smells funny )

Please watch the video see what I see and try to explain.
You don't have a clue what will and won't work with a Scot T and quadrature transformations. Yes, it will work at a max of about 70% efficiency if fine-tuned to the load. You take single phase and make two phase power with a standard phase shift start/run capacitor seen on millions of single phase motors. Once you have the quadrature wave-forms you use that to 'fake' the third phase using the proper mix of wave-forms and transformers to approximate equal voltages and currents in a three phase load.

I don't need to see some random guys video.
 
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Thread Starter

300-3056

Joined Sep 9, 2022
26
This comes back to the whole random guy's video.
I was trying to understand what it was I was looking at.
One single transformer ( pile of scrap ) doing magic that does not seem possible.
As far as I know it simple is impossible to make 3 phase from a single transformer with no amount of capacitors and stuff added.

Yes i know split phase motors are two phase.
I understand what you are saying.
I thought about it... and this is not that.... ( for one thing no single phase motor is here to idle )

That's what I was asking about.
One transformer this honorific hack job....
1662847108700.png

Two or more transformers ( or more winding on multiple cores ) can do a lot of things I know.
Once you have some displacement in phases you do all kinds of shifting you can make 3 into 6, very common.
But this is clearly not a pair of transformers wired up in a Scott T.

I do appreciate your links.
Ill run them buy my young guy and see if he can get me up to speed on the math.
( Still suffering with Laplace when he tried to help me understand math behind governors and feedback. )
 

Thread Starter

300-3056

Joined Sep 9, 2022
26
It's clearly unknown how that transformer(s) is wired above or if it's even part of some 3-phase circuit. I'm not here to judge that video.

https://ieeexplore.ieee.org/document/6367119
https://d3s1jw4anu9c80.cloudfront.net/documents/ADD-A-PHASE-MAN5101.pdf
Ya I know.
I was hoping someone might have some clues or ideas.
I am slowly coming around to the idea that's an auto transformer or reactor.
Its part of a reduced voltage starter, that's the only thing that can explain how it cuts the starting current down so dramatically.

I really do appreciate your attempts to explain two to three with a scott T and some of the other suggestions.
Transformer and motor theory are something I am pretty good with, Calculus not so much LOL.

Thanks again

Nice find on the Ronko thats something familiar worth further investigation.
Just because I want to see it in a print form.
 
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nsaspook

Joined Aug 27, 2009
10,410
Ya I know.
I was hoping someone might have some clues or ideas.
I am slowly coming around to the idea that's an auto transformer or reactor.
Its part of a reduced voltage starter, that's the only thing that can explain how it cuts the starting current down so dramatically.

I really do appreciate your attempts to explain two to three with a scott T and some of the other suggestions.
Transformer and motor theory are something I am pretty good with, Calculus not so much LOL.

Thanks again

Nice find on the Ronko thats something familiar worth further investigation.
Just because I want to see it in a print form.
There's nothing magical with the two core Scott T configuration (you can make one using a single core). The two core version is commonly used because it's more efficient and logical to understand but the same I/Q transform (usually as a RF modulation but can be used at utility line frequencies) can be made from an correctly wired multi coil auto-transformer being the mixer of the two 90 shifted phasors into the resultant third phase.
Phase_shifter_using_IQ_modulator.gif
Animation of a phase shifter using IQ modulator. By changing the amplitude of I and Q waves one can change the phase of the I+Q wave.

https://control.com/textbook/ac-electricity/phasors/

 
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Thread Starter

300-3056

Joined Sep 9, 2022
26
I never seen it done on a single core transformer.
Thank you for the tip.

I have seen done on an internal re connection of a formed coil 2 phase motor running on three phase in a compressor plant.
So old I think Jebus wound it....


Very groovy animation and useful links
Thank you again.

I'm going to scribble out a circuit ( not tonight I'm tired ) of what I seem to recall from an old text book.
I think its a transformer improved rotary, the idea of the transformer is to add some shift to the A phase, B phase is induced and boosted by the transformer and C phase is connect to B phase for balance.
Single phase AC line is supplied to A and C.

When I get my crayons out...
Just pass an eye because something tells me this is not a good idea, and I I think it puts the capacitance on C to B phase in series with the Auto transformer connect from A to B
 
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