Method for fabricating a rotor arrangement and a rotor arrangement for an electric machine

A method of fabricating a rotor arrangement for an electric machine, said method comprising:

• providing a rotor body;
• embedding permanent magnets made from an isotropic magnetic material in the rotor body, each of the permanent magnets having a longitudinal direction and inner and outer ends opposed in said longitudinal direction, the permanent magnets being arranged in a spoke-like manner in pairs of neighboring permanent magnets;
• providing an external magnetizing device comprising a plurality of magnetizing coils which extend obliquely relative to an axial direction of the external magnetizing device;
• arranging the external magnetizing device to be coaxial with the rotor body so that each of the magnetizing coils of said external magnetizing device is positioned opposite one of the pairs of neighboring permanent magnets of said rotor body, the neighboring permanent magnets in each said pair being inclined towards each other so that the outer ends of said neighboring permanent magnets facing the respective magnetizing coil are closer together than the inner ends thereof;
• and
• activating the external magnetizing coils to generate magnetizing flux lines in order to magnetize the permanent magnets with a magnetization that corresponds at least approximately to a Halbach magnetic field distribution, so that the magnetization of each of the permanent magnets is transverse to the longitudinal direction of said permanent magnet;
• wherein, when the external magnetizing device is arranged to be coaxial with the rotor body, the magnetizing coils also extend obliquely relative to the axial direction of said rotor body to generate, when activated, a skew in the magnetization of the permanent magnets along the axial direction of the rotor arrangement.