[Yo-Yo]

Today's wall wart and small brick power supplies (the ones that can use US 120V or European 230V) are called "switching power supplies." They still have a transformer, but it is just much smaller because they work by rectifying the incoming AC to DC, then using a transistor to chop the DC to create AC again but at very high frequencies. The higher the frequency, the smaller the transformer can be made. On the secondary side of the now much smaller transformer, the AC is rectified to DC again, and regulated to the desired voltage (5V, 12V, etc.)

I suppose technically a similar technique could be used at power substations, but it wouldn't be efficient or practical at the very high voltages and power levels required.

[Peet]

On the secondary side of the now much smaller transformer, the AC is rectified to DC again, and regulated to the desired voltage (5V, 12V, etc.)

-=0=- -=0=- -=0=- -=0=- -=0=- -=0=- -=0=- -=0=- -=0=- -=0=- -=0=- -=0=-

Ha ha! You said “rectified”!

Seriously, though... Remember the relatively big selenium rectifiers? I just tossed an old-style battery-charger (auto 6/12 volt) that had one of those in it.

Thank you Bell Labs et.al. for the transistor!