Date of Award

3-12-2020

Publication Type

Doctoral Thesis

Degree Name

Ph.D.

Department

Mechanical, Automotive, and Materials Engineering

Keywords

Noise, NVH, Prediction, Vibration, Vibroacoustics

Supervisor

Colin Novak

Rights

info:eu-repo/semantics/embargoedAccess

Abstract

Vibracoustic noise prediction models for electrically excited cylinders are used to predict the noise emissions for operating dry-type air-core reactors. These reactors are used to limit current and regulate voltage in electrical transmission and distribution grids. During operation, these reactors produce unwanted, electrically induced noise which is created by forced vibration due to the generated magnetic field from the electrical load being applied to the coil. The reactors designed with complex constructions having multiple winding coils will produce greater amounts of structure-borne sound. Given that these dynamically behave as multiple layers of concentric cylinders, cylindrical vibration theory can be used to predict their behaviour. The goal of this research was to construct and validate an innovative vibracoustic prediction model that accurately represents the mechanisms of the structure-borne noise generation of the reactor to accurately predict the noise emission levels during the design phase.For the Trench Limited Coil Operations, having the ability to accurately predict the noise produced by a reactor in the early design stage is critical to maintain a competitive edge in the competitive reactor market by ensuring that acoustic specifications are met. A review of the literature has shown very little work has been done to develop the science to accurately predict the noise generation for complex reactor construction with multiple winding coil packages. Also, the validation process for the current models do not consider a large frequency range and various electrical excitation frequencies. The novelty of this research is the construction of a cylindrical vibroacoustic noise prediction model for complex reactors of multiple winding packages in conjunction with the validation across a wide range of electrical excitation frequencies.In this dissertation, a detailed test and literature review is simultaneously presented in order to guide the development of an improved vibroacoustic model and to validate the noise prediction outcomes. A comprehensive literature review found various vibroacoustic models have been developed to represent the vibrational excitation of the reactor cylinder, and in turn compute the output noise emissions. Comprehensive noise and vibration testing of two prototype reactors with induced electrical excitation was conducted using CPB, FFT, directivity, noise source identification (NSI) and Modal analysis. From these analyses, the construction of the model was guided by considering the natural structural modes. In addition, a bank of noise emission data for validation of the proposed models was complied. Through the validation process of comparing the proposed vibroacoustic models with the collected reactor noise data, a recommended method for noise prediction was developed. The models coined the Cylindrical Vibroacoustic Model (both single and multiple layered models) were deemed to be the most effective and accurate method for reactor noise prediction. The methodology considers the cylindrical construction of the reactor with multiple layers of concentric cylinders and has been validated over a large electrical excitation frequency range. The outcome of this more versatile vibroacoustic model is the ability to better predict the noise emissions for complex reactor constructions having multiple winding coil packages.

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