Patent ID: 6559618
Filing Date: 2003-05-06
Classification: H02P

Abstract:
A control method for electric drive means with induction motors, the method comprising:using a high frequency rotating magnetic field to produce a change of the saturation level of the ferromagnetic core, as a function of the relative positions taken by said rotating magnetic field and by a main magnetic field, and wherein the method comprises at least one of the following phases, taken as single phases or in combination thereof: superimposing a direct or inverse symmetrical set of high frequency voltages to a three-phase stator voltage of an electric machine, so that a zero sequence component of an airgap flux, and consequently a zero sequence stator voltage component and a zero sequence component of the stator current, comprise, besides a third harmonic component, a harmonic with a frequency proportional to the difference between the frequency of a set of three-phase voltages and the frequency of said three-phase stator voltage, or injection of a direct or inverse symmetrical set of high frequency currents or of just one high frequency current along the direction of said airgap flux, these currents are added to the stator current of said electric machine, so that said zero sequence components of the airgap flux, and consequently a zero sequence voltage component and the zero sequence component of the stator current, comprise, besides a third harmonic component, a harmonic with a frequency proportional to the difference between the frequency of said high frequency current and the frequency of said stator current.