Mesh-Type Magnetic Shielding for Audible-Frequency Magnetic Field Ripple Attenuation and NVH Improvement

Magnetic field ripple in the audible-frequency range can induce magnetostriction in ferromagnetic components, causing vibration and noise even in non-rotating systems such as electric vehicle battery systems. Magnetic shielding can reduce such excitation; however, shielding materials used in this range are generally ferromagnetic and may themselves undergo magnetostriction, potentially degrading NVH performance. Therefore, magnetic shielding materials should provide effective field attenuation while suppressing their own vibration to improve system-level NVH performance. In this study, a magnetic shielding test setup and an electromagnetic finite-element model were developed. The electromagnetic model was compared with experimental plate-shield measurements and subsequently used for comparative investigations of the effects of shielding configuration, open-area ratio, and thickness, while the associated NVH performance was evaluated experimentally. A mesh-type structure with a continuous magnetic flux path achieved shielding performance comparable to that of a plate-type structure. Experiments using a 0.635 mm steel-wire mesh provided a magnetic shielding effectiveness of approximately 3.73 dB at 3 kHz and reduced the target vibration component at 6 kHz by 55.8% and system noise by 5 dB. These results demonstrate that mesh-type magnetic shielding can attenuate audible-frequency magnetic field ripple while improving system-level NVH performance, indicating potential application to electric vehicle battery systems and other electromagnetic systems.