Greg Kulibert wrote: I don't know about the jet in particular but many of
the low HP variable speed motors were actually universal motors with a
"voltage regulator" to control the speed. (clip)
^^^^^^^^^^^^^
I have not seen the new Jet minilathe, but I will make the following comment
.. If, by "voltage regulator," you mean a variable voltage power supply, I
would bet dollars to doughnuts that's not what they do. More likely, they
use the type of control that is commonly used to control the speed of
routers: a solid-state circuit cuts down the width of the AC sine wave, to
reduce the on-time per cycle, without reducing the torque. Many of them
also use a feedback loop to sense any speed reduction, and correct it.
These are not expensive, and they produce good torque throughout the speed
range.

Variable frequency three-phase systems are quite expensive, and would not be
appropriate on a mini-lathe.