A Study on the Design of Industrial Servo Motor Using Anisotropic Bonded Magnets

초록

This paper proposes a high-performance servo motor design to suppress control instability caused by harmonic components of the induced voltage in the In-Out Core (closed-slot) stator, using anisotropic bonded magnets without heavy rare-earth elements. The In-Out Core stator improves slot fill factor in small motors, enhances winding manufacturability, and reduces cogging torque. However, it introduces harmonic components in the induced voltage due to flux circulation around the slot region. To address this, a method was applied to increase air-gap flux density and saturate the slot opening region, making it electromagnetically behave as if no slot opening exists. Harmonic characteristics of surface-mounted permanent and interior permanent magnet rotor structures were analyzed, showing that both magnet thickness and sufficiently high remanent flux density are critical for harmonic suppression. As bonded magnets without heavy rare-earths limit remanence, a flux-concentrating spoke-type rotor was applied.

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