通过测试和复特征值法仿真分析新能源汽车用直流有刷电机，发现碳刷和换向器间的摩擦系数影响系统振动模态，从理论上解释了产生电机尖叫噪声的原因。当超过临界摩擦系数时，系统会产生模态耦合效应导致振动不稳定，使电机碳刷系统产生尖叫噪声。通过更改碳刷弹片结构设计，降低了摩擦系数对系统的振动不稳定影响的敏感性，解决了碳刷尖叫噪声。该研究为解决直流电机碳刷尖叫噪声提供了指导和理论支持。

Through test and complex eigenvalue analysis of DC brush motor used in new energy vehicle, the effect of the friction coefficient between commutator and brush on the vibration mode of the brush system is found, and the mechanism of the motor squeal noise is explained theoretically. When the friction coefficient reaches a critical point, the modes couple, leading to vibration instability and consequently the squeal noise of the brush system. After modification of the structure of the brush spring, the effect of friction coefficient on vibration instability becomes less sensitive and the brush system squealing noise is ameliorated. This study provides guidance and theory to solve the brush squeal noise of DC motors.