A HARMONIC PEAK REDUCTION TECHNIQUE FOR OPERATIONAL MODAL ANALYSIS OF ROTATING MACHINERY

In the case of rotating machinery that is operating at constant rotational speed, Operational Modal Analysis is sometimes a challenge due to the presence of significant harmonic peaks. In many cases, the rotating components affect the full frequency range being analysed due to the presence of additional orders. In this paper, a harmonic peak reduction method is presented. The method directly subtracts the harmonic content from the raw time signal. A Gauss-Newton fitting algorithm is used to find the least square reduced fitting of the measurement data to a harmonic deterministic function. The method is tested on two examples. The first is a simple aluminium plate excited with random as well as sinusoidal excitation. In this case, the harmonic peaks are completely removed. The second example consists of noisy measurements from a Prolec GE transformer. In this case, the harmonic reduction method is capable of reducing the harmonic peaks with more than 40 dB on an average.