NVH Performance of Permanent Magnet Synchronous Motors with Liquid Cooling System

The aim of the article is to evaluate the effect of the cooling system on the NVH behavior of traction permanent magnets synchronous motors (PMSMs). An effective numerical method is proposed for modeling the fluid-structure interaction in the cooling system of PMSMs. A simplified physical prototype of a cooling jacket of a PMSM is realized by welding two concentric tubes with an internal cavity filled by coolant. A finite element model of the structure is realized. The coolant is modeled as an acoustic domain to account for the fluid-structure interaction in the cavity and a coupled acoustic-structural dynamic problem is solved. The model is validated by experimental modal tests conducted on the prototype of the cooling jacket both with and without the presence of coolant. The validated model is employed to quantify the effect of the cooling system on a real PMSM. The structure of a 10-poles, 12-slots electric machine is modeled by means of finite element method. The model includes the validated cooling jacket and the internal stator lamination and windings. Numerical vibroacoustic analyses have been performed at different operating conditions, either with or without modeling the coolant with the aim of quantifying its effect on the sound emission of the machine. Acoustic emission is generally increased when fluid coolant is present. For a PMSM, localized sound emission peaks appeared in the low-frequency range, up to 2000 Hz. A maximum increase of 44 dB was observed.