Abstract: To investigate the periodic synchronous vibration fluctuations in turbine generator unis, the thermal shock effect caused by rub between carbon brushes and slip ring was considered. A coupled dynamic equation of bending and thermal deformation was established in the rotating coordinate system. The mechanism of periodic vibration and its influencing factors were analyzed based on the eigenvalue properties of the coupled dynamic equation. The research indicates that under synchronous forward precession, the contact point be-tween the carbon brush and the shaft of the turbine generator is fixed. The heat generated by rub is transferred to the shaft, creating a temperature difference across the section, which excites the vibrational fluctuations. The damping force model is used to establish the rub force equation between the carbon brush and the slip ring. The vibration rotation direction obtained from this is the same as the rotation direction when the rotating speed is below the critical speed, and opposite to the rotation direction when the rotating speed is above the critical speed. This model can explain this type of rub induced vibration phenomenon quite well. When operating within the resonance region, increasing damping can effectively reduce vibration fluctuations. When operating outside the resonance zone, the effect of increasing damping is limited. It is necessary to strengthen the ventilation and cooling of the slip ring, appropriately reduce the contact pressure between the carbon and the slip ring, and reduce the friction coefficient between the carbon brush and the slip ring, as well as between the carbon brush holder.

Key words: turbine generator, vibration, rub, thermal bend, fault diagnosis

摘要： 为了研究汽轮发电机组上发生的工频振动周期性波动现象，考虑碳刷与滑环轴摩擦引发的热冲击效应，在旋转坐标系下建立弯曲和热变形耦合动力学方程，根据耦合动力学方程的特征值性质分析周期性振动机理及其影响因素。研究表明，同步正进动下汽轮发电机碳刷架和转轴之间的接触点固定，摩擦产生的热量传递到转轴上，形成截面温差，激发出振动波动。引入阻尼力模型建立碳刷架和滑环截面摩擦力方程，由此得到的振动旋转方向在临界转速之前和转动方向相同，在临界转速之后和转动方向相反，能比较好地解释这类摩擦振动现象。临界转速区域内增大阻尼可以有效地减小振动波动，临界转速区域之外增大阻尼所能取得的效果有限，需要加强滑环部位通风冷却，适当减小碳换和轴之间的接触压力，减小碳刷和滑环轴截面以及碳刷架之间的摩擦系数。

关键词: 汽轮发电机, 振动, 摩擦, 热变形, 故障诊断