On 31/10/2020 08:34, Harry Bloomfield wrote:
It happens that Brian Gaff (Sofa) formulated :
If he had one why bother with the device, unless its some kind of slow
starter circuit to lessen the load at start up.

Maybe to be able to vary the motor speed?

Or he might have access to 3-ph, though no 3-ph on the site where the
motor is.

All electric motors are in the end synchronous AC motors. In a typical
DC motor or 'universal' AC/DC motor the synchronous AC is created by a
mechanical commutator. This commutator may be replaced at some gain in
efficiency by an electronic inverter, either controlled by a sensor on
the motor or by sensing voltage and current in the windings.

A normal synchronous 3 phase mains AC motor suffers from the inability
to deliver decent torque at anything except its rated RPM. The use of a
variable frequency electronic inverter removes this limitation.

--
Ideas are more powerful than guns. We would not let our enemies have
guns, why should we let them have ideas?

Josef Stalin