Impact Of Electrical Noise On The Torsional Response Of VFD Compressor Trains
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The popularity of VFD motors in compressor trains has increased in recent years. Increased process flexibility is a primary consideration for implementation of VFD systems. However, this comes at a cost of increased mechanical and electrical complexity. Problems rarely experienced with single speed motors have become more likely with VFD's. These include impacts on the torsional behavior leading to component failure and extended downtimes. VFD's can excite the torsional system in several ways. This paper examines the impact of white noise on the torsional response of VFD compressor trains and contrasts it against the response to single frequency harmonic excitation. The characteristics of white noise, noise modeling characteristics for torsional response, and noise generation techniques are examined. Generation of a frequency banded noise signal is presented using a commonly used math modeling code. Two case studies are presented representing VFD compressor trains found in the LNG industry. Both experienced torsional problems related to the VFD and, in one case, led to a coupling failure and release of parts from the train. In the examination of these trains, a single frequency harmonic (SFH) sweep and banded Gaussian white noise (GWN) encompassing the dynamic response envelop of the 1st TNF, are used as inputs to the torsional analysis.
Kocur, John A.; Muench, Maximilian G. (2012). Impact Of Electrical Noise On The Torsional Response Of VFD Compressor Trains. Texas A&M University. Turbomachinery Laboratories. Available electronically from