Good solid VARIAC i call it.
Works as an auto transformer with a variable output.
I have a couple 10 Amperes 2.2 kVA at home for testing power transformers etc, these were dumped by our local POCO from obsolete metering test equipment, happened to be at the right place at the right time.
They usually go to the normal mains voltage and a bit more.
For 110 they go up to 130 Volts.
For 220 they go up to 260 volts.
I always turn the knob about 10% from zero point.
Sometimes the inrush current can trip the MCB at switch on.
