Variable speed controllers do exist for single-phase motors, but they are
relatively expensive.
I found several products a number of years ago, just because I was curious,
as several comments here in RCM (back then), stated that single-phase motors
could not be speed controlled/regulated.
I don't recall the products' makers now, but the controllers weren't
intended to be connected to just any common motors, such as split-phase
types, although I'm fairly certain that the specific motors were not the PSC
permanent-split-capacitor types.

However, PSC motors are controllable with variable speed drives that are
made for PSC motors. Oriental Motor (Japan) makes many models of speed
controlled PSC motors and controllers, which are generally under 1/8 HP
(lots of gearmotors where torque is increased by gear reduction).
PSC motors can be controlled to run over a wide speed range.
The AC capacitor used with PSC motors is typically a small value (under
20uF, sometimes single digit), and is wired full-time in series with one of
the motor's two windings.
When the capacitor is rewired differently (permanently or with an external
switch), the motor rotation is reversed.
One of the features of PSC motors is that they can be quickly reversed by
switch motion (unlike split-phase motors which need to be stopped to reverse
them).

Split-phase motors, with their separate start and run windings and
centrifugal switches aren't easily speed controlled, because slowing the
rotor to a point where the centrifugal switch closes again (start winding
energized again) is a bad idea.

--
WB
..........


"Bob Engelhardt" wrote in message
...
Winston wrote:
...
I don't know anything about this stuff.
Does any of this make sense?

Your translation is very understandable - I commend you for your
perseverance. As to whether it means the same as was written, I dunno.
And as to whether it is reasonable, I have my doubts. The conventional
wisdom is that single phase motors can only be run within small variations
of their natural speed. If this device can do what your translation says,
they have a breakthrough product! I'm not going to be the one who buys &
tries.

Bob