Electronically-commutated motor

Abstract

The motor has a stator and a rotor. One of the elements has coils constituting a three-phase winding and an electronic control module having inputs connected to rotor position sensors and to a speed reference signal (Vc), and including a power circuit for powering the phases from a DC source under the control of a processor. The processor causes the phases to be powered at variable duty ratio so as to regulate speed in a first mode without overlap in time between the periods in which the various phases are powered with voltage pulses, and in a second mode in which there is 33% overlap of power to two phases, and it causes a changeover from the first mode to the second mode when the duty ratio reaches a predetermined value lying in the range 70% to 100%, and a changeover from the second mode to the first mode when the duty ratio falls below another predetermined value.

Dependencies are inferred from the claim text.