Patent ID: 6388405
Filing Date: 2002-05-14
Classification: H02P

Abstract:
A brushless motor comprising:an assembly of a stator and a rotor which has coils constituting a three-phase winding and an electronic control module having inputs connected to rotor position sensors and to an input receiving a speed reference signal, and including a power circuit for powering the phases from a DC source under the control of a processor, wherein said processor is arranged: for powering the phases at a variable duty ratio to regulate speed in a first mode without time overlap between periods during which the phases are fed with current pulses, and in a second mode in which power supplies to two phases have an overlap of 33%; and for causing a changeover from the first mode to the second mode when the duty ratio reaches a first predetermined value lying in the range 70% to 100%, and a changeover from the second mode to the first mode when the duty ratio drops below another predetermined value.