Patent ID: 8183805

Claim:
A system for controlling the steady state rotation of an electric motor (M) of the synchronous type comprising: an electronic switch (TR) operatively connected in series to a stator winding (W) of the motor (M), between a first and a second terminal (A, B) intended to be connected to an alternating voltage supply source, first detector means capable of providing a signal (V oi ) indicating when the current (I) in that winding (W) is zero, and control means (MC) connected to the first detector means and designed to control the electronic switch (TR) in such a way as to cause an alternating current (I) to pass through the stator winding (W), said current (I) having the same frequency as the supply voltage (V) and having portions (I 1 , I 2 ) which are alternatively positive or negative, separated by periods during which it remains at zero; the system comprising: second detector means capable of providing the control means (MC) with a signal (V w ) indicating the magnitude of the supply voltage (V), and in that the control means (MC) are designed to cause a duration (t p ) of said separation periods to vary according to an increasing function of the magnitude of the detected supply voltage (V).