Vibratory response of stator cores of large induction motors operating in an offshore installation.

Lucas, Margaret

Abstract

The work presented in this thesis is based on theoretical and experimental investigations into the vibration behaviour of stator assemblies of induction motors. The aim is to evaluate the effectiveness of using the Finite Element Method to predict the natural frequencies, mode shapes and vibratory response of a large induction motor stator on an offshore installation. This information of stator vibration behaviour is a prerequisite for the installation of a reliable vibration monitoring strategy to detect motor faults. Initial studies are based on the analysis of a small (11 KW) motor stator under free and mounted conditions so that a realistic mathematical representation of a motor stator can be verified by comparing calculated with measured dynamic characteristics. The next stage of the project was to design and develop an original test rig which was a scaled down model of a large (2 MW) induction motor stator assembly. A combined theoretical and experimental investigation of large motor stator dynamic behaviour was carried out and calculated results from a finite element analysis were compared with laboratory measurements. The finite element models were then developed to include response calculations and the vibration amplitudes due to a simple external forcing function and the fundamental electromagnetic radial forcing function were calculated. Measured response levels were recorded on the frame and core of the test rig for comparison. Finally an experimental investigation was carried out into the effects of a single-phasing fault on the vibration signal measured on the core and frame of the large stator assembly model. The main conclusion drawn from this study is that the Finite Element Method is an effective approximation technique for calculating the vibratory response information necessary for reliable motor fault detection by stator assembly vibration monitoring.

Citation

LUCAS, M. 1986. Vibratory response of stator cores of large induction motors operating in an offshore installation. Robert Gordon's Institute of Technology, MPhil thesis. Hosted on OpenAIR [online]. Available from: https://doi.org/10.48526/rgu-wt-1993236

• Thesis Type: Thesis
• Deposit Date: Jul 31, 2024
• Publicly Available Date: Jul 31, 2024
• DOI: https://doi.org/10.48526/rgu-wt-1993236
• Public URL: https://rgu-repository.worktribe.com/output/1993236
• Award Date: Sep 30, 1986