REDUCTION OF THE TORQUE RIPPLE IN SYNCHRONOUS RELUCTANCE MACHINES

REDUCTION OF THE TORQUE RIPPLE IN SYNCHRONOUS RELUCTANCE MACHINES

CHALLENGE

A synschronous reluctance motor is a syncrounous machine, which typically consists of a rotor and a stator. The stator is charachterized by a certain number of slots and a certain winding topology, needed to create a nearly sinusuoidal magnetic field distribution. The non-excited rotor consists of a geometrical arrangement of air gaps, acting as barriers for the magnetic field flux. Due to different reluctances in the rotor, this machine type produces electromagnetic torque as soon as a magnetic field - caused by stator windings - occurs. The application of synchronous reluctance machines is limited by the produced torque ripple. It is estabilished, that the geometry of the rotor flux barriers can be crucial for the torque ripple reduction. Different designs of the flux barriers in the rotor have been proposed to meet this challenge. But more often than not, the known methods have disadvantages with respect to either the mean output torque or the machine’s manufacturing process.

INNOVATION

This invention consists of a particularly advantageous rotor gaps arrangement of a reluctance machine. In this arrangement, the flux barries are rotated at different angles with respect to the axis on the radial direction of the rotor (see the figure below). This arrangement has the following advantages:

  • The reduction of the torque ripple can be obtained for all stator and rotor geometries;
  • Torque ripples can be reduced by up to 54% (depending on the machine design);
  • Average output torque remains nearly constant (1-2% decrease compared to standard motors);
  • The fabrication of the rotor is comparatively easy, because the flux barriers are identical besides their rotation with respect to the axis.

COMMERCIAL OPPORTUNITIES

The invention can be used for a wide range of applications, where an electric motor or generator is implemented. Some examples are the electromobility, energy generation (wind energy), and pumping systems.

(a) Exemplary arrangement of the flux barriers according to the invention; two of the barries are rorated by a certain angle (labeled as α1 and α2, respectively) with respect to the axis in the radial direction. (b) torque of a synchronous reluctance machine with a 12-teeth-stator and 4-poles-rotor (12/4-SynRM) either according to the standard arrangment (blue line) or according to the arrangement developed in the frame of the invention (red line); the torque ripple is reduced by the 38%, while the average torque (red dashed line) is only 2% smaller in comparison with a standard machine (blue dashed line). (c) torque of a synchronous reluctance machine with a 42-teeth-stator and 14-poles-rotor (42/14-SynRM) either according to the standard arrangment (blue line) or according to the arrangement developed in the frame of the invention (red line); the torque ripple is reduced by the 54%, while the average torque (red dashed line) is only 1% smaller in comparison with a standard machine (blue dashed line).

REFERENCES

[1] DE 10 2016 211 841 A1, WO 2018/002128 A1

Dr. Tobia Mancabelli
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tmancabelli@baypat.de
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