The mysterious street transformers of Saigon

If you’ve been to Saigon, then you know how it is. The city is filled with hundreds and hundreds – if not thousands – of above-the-ground transformers that look like this:

Now, I am not an electrician, so I could be wrong, but it looks as though these units are converting three phase electricity to two phase electricity, as this close up shows:

What are these transformers here for?  What do they do?  Are there indeed underground three-phase electrical cables – which in and of itself would be an amazing thing?

For me this is still just a mystery to be cleared up one day!