Noise, Vibration, and Harshness Countermeasures of Permanent Magnet Synchronous Motor with Viscoelastic Layer Material

An electric motor exhibits structural dynamic excitation at high frequency, making it particularly prone to noise, vibration, and harshness (NVH) problems. To mitigate this effect, this article discusses a novel countermeasure technique to improve NVH performances of electric machines. A viscoelastic rubber layer is applied on the outer surface of a permanent magnet synchronous motor (PMSM) as vibration damping treatment. The goal is to assess the countermeasure effectiveness in reducing acoustic emissions at different temperatures, through a combination of numerical modeling and experimental validation. A finite element model of the structure is realized, considering a viscoelastic material model for the rubber material, with frequency-dependent loss factor and storage modulus. The numerical model is validated by means of experimental modal tests performed on a house-built cylindrical structure, designed to mimic the geometry of a typical cooling jacket of a PMSM for automotive applications. The structure of a 10-pole 12-slots electric motor and the validated cooling jacket are modeled using finite element method (FEM). Vibro-acoustic simulations were carried out both with and without the presence of the viscoelastic damping layer. Results demonstrate that the application of the viscoelastic layer effectively reduces acoustic emissions, achieving a reduction of 9 dB.