馬達臨界轉速之測量及模態測試

Measurement of Critical Speed and Modal Testing for Motor

賴建宏(Chien- hung Lai)

指導教授 ： 康淵 ； 張永鵬

中原大學/工學院/機械工程研究所/碩士(2002年)

https://doi.org/10.6840/cycu200200571

摘要

本文之研究目的為以實驗測量工業用的馬達臨界轉速以建立共振頻率的判讀方法。針對東元電機公司所生產之工業用馬達，使用頻譜分析儀、加速規、轉速計、位移計、衝擊錘等測量儀器進行共振測試。使用的共振分析方法有兩種 1.由頻譜分析儀量測馬達在加速或減速過程中之頻線瀑布圖(Waterfall) 2.使用頻譜分析儀量測激發響應所得之頻率響應函數(FRF)的模態測試方法。
當使用頻線瀑布圖測試方法時，至少需連續作三次以上，並重複出現同一振峰，並在振峰之前，倍頻列呈現峰值成長，之後峰列呈現消減，即可認定此振峰為共振頻率。由於瀑布圖易受雜訊影響且重現性差，又無法以多次平均的方式來去除雜訊，因此只能用以判斷有明確共振時的臨界轉速。
在無法確認工作轉速內是否有共振發生，或是要確認更高轉速之共振時，則必須進行模態測試來確認共振的發生位置。使用模態測試方法可以得到各量測點的頻率響應函數，經由模態分析後可以得到模態振形，以確認共振頻率的模態歸屬，進而分離出馬達轉子共振、馬達框架的共振或是兩者的耦合共振。

關鍵字

瀑布圖 ； 模態測試 ； 臨界轉速

並列摘要

The major purpose of this study is concerned of experimental methods to measure the critical speed with resonant frequency. The FFT analyzer, accelerometer, tachometer, proximeter and impulse hammer are applied to resonant test on TECO motors. Two methods adopted here for resonant test are ： 1. measuring the waterfall during operation with speed star-up or coast-down in motors with FFT analyzer. 2.measuring the modal test of frequency response function from excitation response with FFT analyzer.
Once the waterfall testing method is employed, the same peak of amplitude must be occurring repeatedly at least three times of each operation and harmonic series amplitude growing before the peak and diminishing after the peak. Hence, the peak of amplitude can be indicated as resonant frequency. On account of the less repeatability and effect of noise not eliminated by multiple averaging method, the waterfall only can be used when there exists critical speeds with resonant frequency.
The modal testing method must be introduced to confirm the positive position of resonant frequency, due to the unpredictable excitation response in working speed and on highly rotating speed of operation. Hence, the frequency response function on each measuring spot can be obtained through modal analysis and classified resonance frequency and mode shape can also be described as to differentiate the resonant or the coupling resonance of motors rotor and frames.

並列關鍵字

waterfall ； critical speed ； modal testing

參考文獻

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