摘要：模态分析是一种能够确定结构振动特性的技术，为了降低永磁同步电动机的电磁噪声有必要分析和计算机座的振动模态。本文针对一台20 kW变频起动永磁同步电动机，应用Workbench有限元软件对电机机座的模态进行了仿真分析，分析了散热筋、底脚、端盖、接线盒和电机底脚在约束的情况下分别对电机机座固有频率的影响，通过三维有限元仿真得到机座结构径向各阶模态的固有频率和模态振型，找出了不同结构部件对电机机座固有频率影响规律，对研究如何防止电机共振，降低永磁电机的电磁噪声具有指导意义。

关键词：模态分析；有限元；固有频率；模态阵型
Abstract: Modal analysis is a technology for vibration characteristic research. In order to reduce electromagnetic noise of  permanent magnet synchronous motors, it is essential to analyze and calculate the vibration modal of the motor frame. In this paper, for a 20 kW variable frequency start permanent magnet synchronous motors, apply finite element software called Workbench to simulating and analyzing the modal of motor frame. Analyze the influence of cooling ribs, feet, end caps, junction box and restriction of motor feet to the natural frequency of the motor frame. Find out the rules of natural frequencies that different structure components affect on by using 3D finite element simulation to obtain the natural frequencies of radial each order modals and modal shapes. It is significant for how to prevent the resonance and reduce the electromagnetic noise of the permanent magnet synchronous motors.

Key words: modal analysis; finite element; natural frequency; modal shape