大功率高速永磁电机柔性转子系统模态分析

Modal Analysis of the Flexible Rotor System for High-Power High-Speed Permanent Magnet Machine

高速电机的转速高、转子细长,与常速电机相比接近临界转速的可能性大大增加,当电机额定转速接近临界转速时,电机会发生剧烈的振动,甚至使转子损坏。大功率高速电机的转子长度远远大于转子直径,很难设计为刚性转子,需要穿越1阶临界转速,工作在1阶临界转速和2阶临界转速中间的安全区域,而这个安全区域的范围却很小,这对大功率高速电机转子系统的动力学设计带来了极大的困难。基于一台1.12MW、18 000r/min的高速永磁电机,对转子系统的动力学特性进行理论分析,对有叶轮和无叶轮状态下的转子模态和临界转速进行计算,分析轴承支承刚度、陀螺效应以及转子主要尺寸对临界转速的影响,并通过样机进行了实验验证,总结了相应的规律,为大功率高速电机挠性转子的设计提供了参考。

For high speed machine, it is far more vulnerable when the rated speed close to critical speed. Under this circumstance, severe vibration will occur and even damage the rotor. For high-power high-speed machine, the rotor length is much greater than the diameter of the rotor. It needs to be designed as a flexible rotor system. The rated speed passes through the first-order critical speed, working in the security zone between the first-order critical speed and the second-order critical speed. But the scope of this security zone is very small, which brings great difficulties in designing high-power high-speed motor rotor system. In this paper, based on a 1.12MW, 18 000r/min high-speed permanent magnet （PM） machine, the dynamic characteristics of rotor system are analyzed theoretically, while the rotor modal and critical speed are also calculated. And then, the influencing factors on rotor critical speed are analyzed, including bearing stiffness, gyroscopic effect and the rotor main dimensions. Finally, a prototype is manufactured and a rotor vibration test is developed. The experimental results have validated the rotor critical speed analysis. It would provide the reference to rotor system design for high-power high-speed machine.