Modal Analysis of An External Rotor Machine For Electric Propulsion Aircraft

It is the electromagnetic vibration noise of permanent magnet synchronous machine (PMSM) that is closely related to the modal calculation of the machine structure. An accurate modal calculation is the basis for the study of the vibration and noise characteristics of PMSM. Modal analysis helps to improve the design of the structure in order to avoid resonance. In this paper, the modal analysis of a propulsion machine for an aircraft was presented. The frequencies and mode shapes of the stator, rotor and the machine are obtained using finite element method (FEM). The results show that the frequencies and mode shapes of stator vary noticeably which is helpful in reducing the system vibration and avoiding resonating resonance. Calculations of the rotor natural frequency, vibration modes and critical speeds were conducted. The frequencies of the structure with more components of the machine are greatly increased in the same order. And the natural frequencies of different orders are quite different from that of the radial electromagnetic force with larger amplitude, so the resonance is effectively suppressed.