Magnetic Anisotropic Properties Measurement and Analysis of the Soft Magnetic Composite Materials

Soft magnetic composite (SMC) material produced by powder metallurgical techniques is assumed to be an isotropic material. It is applied in the core with special structure of rotating electrical machines, in which, the local magnetic flux density varies with time depend on both magnitude and orientation. Magnetic anisotropic feature may be shown in the material and influences the core operational performance. By using the designed 3-D magnetic properties tester, this paper presents the alternating and rotational magnetic properties of the SMC materials. Slightly anisotropic properties are found in hysteresis features and core loss distributions along different magnetization directions or planes. Experimental results show that some direction of the testing specimen seems harder to be magnetized than other directions. Milling and pressing process of the bulk specimen may cause changing of the grain size, micro-strain and pinning. These can influence the coercivity and remanence of the material and cause magnetic anisotropy, which may also be enhanced by increasing frequency and magnetization.