look on youtube squealing pig transverter Mr Grey and his group were working on something like that.

No.  In real 3 phase power each power phase is 120 degrees out of phase from the phase before and the phase after it.  You can't create that from single phase with only transformers.  You can use capacitors to shift the phase enough to fool a 3 phase motor into starting but only if the motor has a small load or no load on it.  Once the 3 phase motor gets up to speed you can then load it to use it for work but the real power of the motor will still be below the normal power it would have if it was connected to real 3 phase power.

Is this what you are referring to?
 Three Phase Transformer & Single Phase Transformer - Former is generally used in three phase power system as it is cost effective than later. But when size matters, it is preferable to use a bank of three single phase transformer as it is easier to transport than one single three phase transformer unit.

This statement does not mean you can convert single phase to 3 phase with 3 single phase transformers.  What they are talking about is to use separate transformers for each phase.  But each of those is fed from a different phase from the generating station.  As I said you cannot generate 3 phase power from using 3 single phase transformers when you only have a single phase source.

(Both have the same kind of efficiency, however working with a 3PH system is more convenient, as you have a rotary field, whilst in the TV you have a static field.

(you could however make a 3PH TV with 3 single phase transformers or with a 3PH transformer)

I don't think you are being a pain.   I think you are just trying to learn.  Unfortunately I don't really know anything about the TV.  I am a little familiar with the rotoverter but never tried to make one.  From the articles you linked to it looks like they are trying to make use of the ferroresonance of the transformer core material.  The Peswiki article is talking about a particular type of transformer used in industry that maintains a fixed output voltage under changing conditions of either load or input voltage.  They can maintain an output voltage of 120 volts under a wide range of load conditions and with an input voltage from 90 to 140 volts or so.  They are a special type of transformer that is also very expensive.  One of those will cost more than a small 3 phase motor.

There is not enough information in the two videos of the guys who made their own transformers to even begin to guess what they are doing.  But it appears they are only using single phase transformers.  I am not sure why you think you need a 3 phase transformer.

From the responses you have gotten on this forum it appears no one else here is familiar with the transverter either.  Maybe someone else will see your posts and add some more information.

The circuits shown in the Peswiki article are all using single phase transformers.   Also the videos you posted links to are also using single phase transformers.  So my guess is while you could possibly use a 3 phase transformer it is not required for the transverter to work.  The Peswiki article does not give the total information needed I feel to get the device to work.  I think at the minimum you will need a very good scope and some accurate meters.  With those and a lot of experience working with resonant circuits you might get it to work.  Also you might need a good capacitance and inductance meter to match up the parts of the circuit to get it to work properly.  I feel like just putting some parts together is not going to be enough to get this circuit to work.  I have over 50 years experience working in electronics and I would hesitate to build this without some more information on exactly how it should be tuned and operated.

I wish you good luck if you decide to pursue this project.

If I can help anymore just ask and I will try to respond.  However after today I will not have internet access for a few days so my response may be a little slow.

Carroll