The Importance of Structural Modal Analysis in 2 Poles Induction Motors for LNG Application

Abstract

Case Study 18: High vibrations due to 2X electrical frequency excitation on bearing housings and frame occurred on a 20MW 2-Pole Induction Motors during acceptance tests in manufacturer workshop in stand alone configuration. Modal Analysis results in Factory Acceptance Tests (FAT) configuration were confirmed by Operating Deflection Shape (ODS) and Experimental Modal Analysis (EMA - Hammer test) leading to supports redesign. To mitigate the risk of high vibration in string test bench and customer site, validating also the present motor design, a further Modal Analysis were executed using the experimental data collected during the FAT to drive mode selection.