How can we get 1-phase 240v from 3-phase 11kV transformer?

In Europe we have a 1-phase 220v/240v power supply to home, which is ONE hot line, unlike America that have TWO hot lines (120v of each) into their homes which is therefore logically and technically a 2-phase power supply, even if they will admit the obvious.

There are two ways we can be feed our 1-phase supply from the pole mounted 3-phase 11kV line. The primary of that transformer can be feed from either one of the 3-phase lines, that would be 6.4kV to Earth, or feed from two of the 3-phase lines, that would be 11kV.
Split the 240V phase into TWO phases 120v
There is no real difference, just requiring the correct Transformer Primary voltage. But by using two of those lines, feed into a single winding Transformer, then there is no need for the power supply company to include a Neutral wire along the pole route.

This is exactly the same as done in America, except the 240V Secondary of that Transformer is center tapped, to Split the 240V phase into TWO phases 120v, at 180° from each other. Then they feed those TWO 120v hot wires and the Neutral into homes. But in most of the World, there is only ONE 240v hot wire feed into every home with the Neutral.

It can happen unbalanced currents in the 3-phase power supply, but the power supply companies try to distribute evenly from all 3 wires of their 3-phase 11kV supply. They don't always get it exactly right, but they do try to get the balance fairly close, by connecting those Transformers across different 11kV phase wires. Just remember, the 240V Live wire in your home, may well have significant voltage difference, from a neighbor of yours, if they are feed from a different pole Transformer, that is feed from different 11kV wires to yours. It is not a different Voltage, you both have 240V, but may be at a different phase relationship, if sourced from different 11kV phase wires. If you walk down the road, looking at different pole Transformers, then you should see they are feed from different 11kV phase wires. So hopefully, overall they should get a fairly reasonable balance. But the supply company does have to allow for some unbalanced current flow.

You should also notice that the power supply companies have earthed the Neutral, in the ground below the pole. And that common Neutral/Earth (TN-C) wire should also be earthed at every house feed by that Transformer. Perhaps not often done in homes, but it is good to add more earthing rods. I have got one property Neutral wire, down to better than just 2 Ohms from the soil around my house. Then in your Home, your distribution should separate the Neutral wiring from the Protective Earth wiring.

You may need a voltage transformer for converting 110v to 220v between Europe and America.

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2/4/2018 12:58 PM